This document provides an overview of laboratory investigations. It begins by outlining the need for lab investigations to supplement clinical findings. It then defines lab investigations and discusses their generic applications and classifications based on location, specificity/sensitivity, and frequency of use in dentistry. The document goes on to cover crucial questions to consider prior to ordering lab tests and provides examples of commonly used hematological, biochemical, microbiological, immunological, and histopathological investigations. It concludes by discussing common clinical scenarios where lab tests are useful.

1. LABORATORY
INVESTIGATIONS
SAURABH ROY
24.08.2015
1

2. Contents:
1. Need for Lab investigations
2. Definition
3. Generic Applications
4. Classifications
5. Crucial Q&As prior to Lab Investigations
6. Laboratory Investigations(Frequently and infrequently required)
a. Haematological Investigations
b. Biochemistry Investigations
2

3. Contents:
c. Microbiological Investigations
d. Immunological Investigations
e. Histopathological and Cytopathological Investigations
7. Common Clinical Scenarios
8. Conclusion
9. References
3

4. Need for:
 Evidence shows Case History and Clinical examination usually
reveal most if not all of clinically relevant data
 Hence there remains a need to confirm our clinical impression
 Lab investigations supplement rather than replace other methods
for gathering information
 It is a known fact that with the help of lab investigations, some
underlying systemic conditions of which the patients are unaware
of, are often identified in dental practice for the first time
4

5. Definition:
Laboratory studies are an extension of physical
examination in which tissue, blood, urine or other
specimens are obtained from patients and subjected to
microscopic, biochemical, microbiological or
immunological examination.
Information obtained from these investigations help us in
identifying the nature of the disease.
5

6. Generic Applications:
 Confirming or rejecting clinical diagnosis
 Providing suitable guidelines in patient management
 Providing prognostic information of the diseases under
consideration
 Detecting diseases through case-finding screening methods
 Establishing normal baseline values before treatment
 Monitoring follow up therapy
 Providing information for Medico-Legal consultations
6

7. Classifications:
 Based on where investigation is done:
Chair side
Investigations
Laboratory
Investigations
Acts as a precursor to
laboratory investigations
Significantly higher sensitivity
and specificity
Egs : Toluidine blue staining
for grading dysplasia, Electric
Pulp testing for tooth vitality,
Radiographs
Egs: Glycated Haemoglobin
estimation,
Peripheral smear histology
7

8. Classifications:
 Based on specificity/sensitivity:
Screening Tests Diagnostic Tests
An ideal screening test is 100%
sensitive
An ideal diagnostic test is 100% specific
Useful in a large sample size at
risk; typically cheaper
Useful in symptomatic individuals to establish
diagnosis or asymptomatic individuals with +ve
screening test; expensive
Egs : blood glucose estimation for
screening diabetes,
Haematocrit values for anaemia,
VDRL test for syphilis
Egs: Glycated Haemoglobin estimation, OGTT
Peripheral smear histology,
FTA-Abs test for syphilis
8

9. Classifications:
 Based on Hospital Lab Services:
Haematology Microbiology Biochemistry
Immunology Histopathology Cytopathology
9

10. Haematology:
 Deals with investigations of abnormalities of blood cells, their
precursors and of the haemostatic & clotting mechanisms
Microbiology:
 In this discipline body fluids, mucosal surfaces and excised
tissues are examined by using microscopical, cultural and
serological techniques.
 To detect and identify the causative micro organism
 Eg: Antibiotic sensitivity testing
10

11. Biochemistry:
 Also called chemical pathology
 Deals with investigations of the metabolic
abnormalities of the body in disease states.
 Investigations are carried out by assays of various
normal and abnormal compounds found in body
fluids viz. blood, urine, CSF, saliva etc.
11

12. Immunology:
 Deals with the detection of abnormalities in the
immune system
 Primary role to Identify a disease is by observing
the presence of an antibody in the patient that
resulted from the infection(entry of pathogen)
 The semi quantitative measure of the amount of
antibody present in serum is called a Titre.
12

13. Histopathology:
 Deals with the identification of structural changes in diseased
tissues through microscopic examination of appropriately
stained tissue sections obtained from biopsy procedures.
Cytopathology:
Scientific Study of role of individual cells or cell types in disease.
Clinician collects a sample of abnormal cells from lesional tissue scrapings
or by means of tissue aspiration.
Cells are then stained and studied under light microscopy
13

14. Classifications:
 Based on frequency of dental use: (by Sonis, Fazio & Fang )
Frequently used:
• CBC- Hb, Hct,
Absolute and
differential WBC
• Bleeding studies –
BT,CT, PT, aPTT
• Peripheral Blood
Smear
• Random Blood
Glucose
Occasionally
done:
• Tests for disturbance
of bone – Ca, P, ALP
• ESR
• Urinalysis
• Screening Test for
Syphilis
Rarely ordered:
• Enzyme testing –
CPK, SGOT, SGPT,
LDH
• Bilirubin Estimation
• Creatinine Estimation
• Acid Phosphatase
• BUN
14

15. Crucial Q & As prior to Lab Investigations:
1. For a given situation, WHAT investigation is appropriate?
 Often a dental practitioner is faced with a dilemma of what investigation to
order in a given clinical scenario.
 The plan of investigation should be therefore decided from the facts
obtained from history taking and clinical examination
 Investigations are useful only when the appropriate tests are requested, and
interpreted in the light of history, clinical findings, knowledge and
experience.
 Before any investigations are initiated, Patient Consent must be obtained
15

16. Crucial Q & As prior to Lab Investigations:
2. What sample to be collected for the Test?
 Samples should optimally be the most likely entity which harbours the
causative organism or abnormal constituents of body fluids like
electrolytes, chemical compounds or antigens
16

17. Crucial Q & As prior to Lab Investigations:
3. How to collect specimens?
 Success or failure of the investigation depends on the procedures carried
out in collection, preservation and transport of the specimens.
 In cases of microbiological and culture tests, the specimen must be material
from the actual site of infection and should be collected with minimum of
contamination from adjacent tissues or secretions.
 In cases of tissue collection, the site of collection as well as the vicinity
with respect to the lesion assumes importance
 Apart from this the timing (When??) of specimen collection is also
important
17

18. Crucial Q & As prior to Lab Investigations:
3. How to collect specimens?
 In general specimens collected from swabs are inferior in material
collection when compared to aspirates.
 In cases of collection of blood samples for haematology, it can be collected
either via skin , venous or arterial puncture
 If a clinician wishes to study its cellular components, its important that the
blood sample remain unclotted.
 If blood specimen has been refrigerated, it must be brought back to room
temperature for investigations as cold specimens yield false values.
18

19. Crucial Q & As prior to Lab Investigations:
4. What Information to be furnished to the laboratory?
 Specimens should accompany properly filled out forms from the clinician
 Preliminary details include: Name, Address, Hosp. No. , Gender & Date of Birth
 Other important details are
 Exact nature of the specimen
 Source of the specimen
 Nature of investigation requested
 Date and time of specimen collection
 Brief Clinical Details
 Tentative Diagnosis
 Current Therapy if any
19

20. Crucial Q & As prior to Lab Investigations:
5. Estimated cost and time expense?
 The clinician should comprehensively detail the patient about the cost
aspect of the following investigation in order to allow the patient to make
an informed choice of undertaking it.
 The clinician should also provide a realistic estimate of the time duration
required from the collection of specimen from patient till obtaining the
results and its interpretation
20

21. Crucial Q & As prior to Lab Investigations:
6. Expected risks and discomfort to patient, clinician and personnel?
 The patient must be beforehand explained about the possible risks of the
investigative procedure, if any
 Verbal informed consent is adequate for non invasive procedures, but for
invasive procedures a signed, witnessed and a written informed consent is
necessary.
 All body fluids and tissues are considered potentially infectious.
 Barrier precautions must always be employed to prevent transmission to
other patients or staff during investigations.
21

22. Crucial Q & As prior to Lab Investigations:
7. Interpretation of results?
 Clinician’s knowledge of pathology is essential for interpreting results.
 The clinician should be able to assess the false negative results in non-
quantitative tests
 For quantitative tests, the normal values may vary between different lab
settings. Hence communication with laboratory personnel becomes very
important in these settings.
 It must also be remembered that a value just outside the range of normal
does not necessarily indicate abnormality.
22

23. Lab Investigations(Frequently and
infrequently required): 23

24. Haematological Investigations(Frequently
used) :
 Complete Blood count includes:
1. Hb
2. PCV
3. RBC Count
4. TLC
5. DLC
6. Platelet count
7. ESR
8. RBC Indices
24

25. Haematological Investigations:
 RBC Count:
 Normal range – Adult male : 4 - 6 million cells/cu. mm
Adult female : 3 - 5 million cells/cu. mm
Polycythaemia Anaemia
Abnormally high values of
circulating RBCs; may be primary
or secondary
Abnormally low values of
circulating RBCs
Seen in abnormality of bone
marrow(primary) or altitude
related(secondary)
May result from chronic
haemorrhage, bone marrow
failure(secondary to radiation,
drugs or tumour associated)
25

26. Haematological Investigations:
 Haematocrit (Hct) :
Volume of packed erythrocytes/100ml of blood done in a centrifuge
Although test is inaccurate, it is more precise than the erythrocyte count
and is used in combination with it
Normal range: Adult male : 40-54%
Adult female : 38-47%
In general these values are increased in polycythaemia and reduced in
anaemia.
26

27. Haematological Investigations:
 Haemoglobin(Hb) :
Oxygen carrying component of erythrocytes
Hence, amount of Hb in the RBCs indicates the level at which it can
supply oxygen to the tissues
Normal range – Adult male : 14 -18 g%
Adult female : 12 – 16 g%
Low values indicate anaemia while high values indicate polycythaemia
27

28. Haematological Investigations:
 Peripheral Smear:
Provides info concerning the size and shape of the red blood cells
It may allow
Identification of sickle cell & normocytic, microcytic and macrocytic
anaemia
Evaluation of Hb pigmentation of individual cells to be classified as
normochromic, hypochromic or hyper chromic
28

29. Haematological Investigations:
 Mean Cell Volume(MCV):
Ratio of Haematocrit to RBC count expressed in µm3.
Describes volume of RBC
range:
Normal – 82-92/ µm3
Normocytic anaemia – 82-92/ µm3
Microcytic anaemia – 50-80/ µm3
Macrocytic anaemia – 95-100/ µm3
29

30. Haematological Investigations:
 Mean Cell Haemoglobin(MCH):
Ratio of Hb to RBCs and is expressed in picograms
It expresses the Hb component of each cell
range:
Normal – 27-31 pcg
Normocytic anaemia – 25-30 pcg
Microcytic anaemia - 15-25 pcg
Macrocytic anaemia - 30-50 pcg
30

31. Haematological Investigations:
 Mean Cell Haemoglobin Concentration(MCHC):
Ratio of Hb to Hct
Value expressed as a percentage of volume of red blood cells.
Measures Hb concentration in grams/100ml of packed erythrocytes
range:
 Normal – 32-36%
 Normocytic anaemia – 32-36%
 Microcytic anaemia - 25-30%
 Macrocytic anaemia - 32-36%
31

32. Haematological Investigations:
 Erythrocyte Sedimentation Rate(ESR or Sed Rate):
In certain febrile diseases as well as in others the amount of circulating
fibrinogen is increased
The resultant increased viscosity of blood slows down the sedimentation rate
of erythrocytes
ESR indicates the speed with which the erythrocytes settle in uncoagulated
blood
Values:
 Men < 50 years - <15 mm/hr.
 Women < 50 years - <20 mm/hr.
 Men >50 years - <20 mm/hr.
 Women >50 years - <30 mm/hr.
32

33. Haematological Investigations:
 Erythrocyte Sedimentation Rate(ESR or Sed Rate):
Interpretation:
Raised ESR Lowered ESR
Tuberculosis Polycythaemia
SABE Spherocytosis
Acute MI Sickle Cell Anaemia
Septic Shock Congestive Heart Failure
Anaemia New Born Infant
33

34. Haematological Investigations:
 White Blood Cell Count: (WBC)
The white blood cells or Leukocytes are classified as either
granulocytes or agranulocytes
Normal range: 4500-11000 cells/mm3
High values may be caused by leukaemia, polycythaemia or
infectious diseases
Low values may be due to bone marrow depression, aplastic
anaemia, drug reactions and viral infections viz influenza
34

35. Haematological Investigations:
 Differential White Blood Cell Count: (DLC)
Obtained from a peripheral blood smear
The granular and nongranular leukocytes are counted and its
values are expressed as a percentage of Total WBC
Neutrophils:
Band neutrophils are immature while seg neutrophils are mature
Normal Band value – 2-3% while normal seg value – 50-60%
High Band value may indicate presence of an acute infection while Low
value may indicate bone marrow depression
High Seg values may indicate AML, drug/poison intoxication while Low
value may indicate malignant neutropenia or aplastic anaemia
35

36. Haematological Investigations:
 Differential White Blood Cell Count: (DLC)
Basophils:
Normal value – 0 – 1%
High values uncommon; may indicate myeloproliferative disease
Low values may indicate an oncoming anaphylactic reaction
Eosinophils:
Normal value – 0 – 5%
High values are mostly observed in allergies or parasitic infections
Low values are mostly observed in aplastic anaemia and patients on
cortisone therapy
36

37. Haematological Investigations:
 Differential White Blood Cell Count: (DLC)
Lymphocytes:
Normal value – 30 – 40%
High values may indicate chronic/viral infections, lymphocytic leukaemia
Low values may indicate aplastic anaemia or myelogenous leukaemia
Monocytes:
Normal value – 3 – 7%
High values are seen in Monocytic leukaemia, Hodgkin’s disease, SABE
Low values are mostly seen in aplastic anaemia
37

38. Haematological Investigations:
Bleeding Time:
Measures the time for haemostatic plug formation
Normal Bleeding time – 2-7 mins
Any clotting factor deficiency or platelet abnormality will lead to increased BT
Prolonged in
Thrombocytopenia
Acute leukaemia
Aplastic anaemia
Liver diseases
Von-Willebrand’s disease
38

39. Haematological Investigations:
Clotting Time:
Measures the time required for formation of first clot.
Screening test for coagulation disorders
Normal Clotting time – 4-14 mins
39

40. Haematological Investigations(infrequently
required) :
1. Prothrombin Time (PT):
Time in seconds that is required that is required for fibrin threads to form in citrated or
oxalated plasma
Normal time – 11-14 secs
Measured against a Control PT in terms of INR
INR = PTTest / PTNormal
Normal INR = 1 ; Abnormal INR > 1.5
Measures extrinsic and common pathway – Factors I,II, V ,VII, X
40

41. Haematological Investigations(infrequently
required) :
1. Prothrombin Time (PT):
Increased PT
Disseminated Intravascular Coagulation
Patients on Warfarin Therapy
Vit K deficiency
Early & End stage Liver failure
41

42. Haematological Investigations(infrequently
required) :
2. Activated Partial Thromboplastin Time (aPTT):
 Time in seconds that’s required for a clot to form in citrated or oxalated plasma
Performance indicator of both the intrinsic & common pathways
Typical reference range – 30-40 secs
 Increased aPTT seen in :
Patients on Heparin Therapy
Von – Willebrand’s disease
Disseminated Intravascular Coagulation
Early Stage Liver failure/ Wilson’s disease
Haemophilia
42

43. Haematological Investigations(infrequently
required) :
3. Rumpel-Leede Test(Tourniquet Test):
Test of ability of the superficial capillaries of the skin of the forearm and hand to withstand
an increased intraluminal pressure and a certain degree of hypoxia
Done by occluding veins of the upper arm with a blood pressure cuff for 5 mins.
Indicated in suspicions of bleeding abnormalities, petechiae in oral cavity and scurvy
Presence of >20 petechiae/sq. inch is considered abnormal
Dental Application – screening test for scurvy (Scorbutic gingivitis)
43

44. Haematological Investigations(infrequently
required) :
4. Schilling Test:
It is a measure of the patient’s ability to absorb orally administered radioactive Vit B12
labelled with 60Co
Patients with pernicious anaemia excrete less than 5% of orally administered dose in
comparison with 8-25% by normal individuals
44

45. Haematological
Investigations(infrequently required) :
5. Serum Iron and Total Iron Binding Capacity:
 Iron deficiency is usually detected on the basis of the amount of iron
bound to transferrin in the plasma(serum iron) and the total amount of
iron that can be bound to the plasma transferrin in vitro
 Normal values
 Serum iron – 80-180 µg/dl
 TIBC – 250 – 370 µg/dl
45

46. 46

47. BioChemistry: 47

48. Serum chemistry:
Serum is that portion of blood remaining after whole blood has been
allowed to clot
Responsible for fluid maintenance Intra and extra cellularly
Responsible for the optimal osmotic gradient, nerve and muscle
function and hydration
48

49. Serum chemistry(frequently used):
1. Blood Glucose estimations:
Fasting Blood Sugar(FBS): Normal values – 70-90 mg/100ml
Random Blood Sugar(RBS): 110-130 mg/100ml
Post Prandial Blood Sugar(PPBS): <140 mg/100ml
High values are seen in Diabetes mellitus, Cushing’s disease,
pheochromocytoma, in patients taking corticosteroids
Low values seen in insulin secreting tumours, Addison’s, Pituitary hypo
function
49

50. Serum chemistry(frequently used):
2. Oral Glucose Tolerance Test:
2. Used for the definitive diagnosis of diabetes mellitus and for
distinguishing diabetes from other causes of hyperglycaemia like
hyperthyroidism
3. Should be performed on only healthy ambulatory patients who are
not under any drugs which may interfere with glucose estimation
4. Oral Glucose Challenge: explain
5. OGCT(challenge Test) is a short version of OGTT used in pregnant
women to check for Gestational Diabetes
50

51. Serum chemistry(frequently used):
Oral Glucose Tolerance Test:
Criteria for Interpretation:
1. Fajans and Conn Criteria
2. Wilkerson Point System
3. The University Group Diabetes Program Criteria
51

52. Serum chemistry(frequently used):
Oral Glucose Tolerance Test:
Fajans & Conn Criteria:
Abnormally increased values of any 2 parameters indicate diabetes
Fasting Blood Sugar > 100 mg/dl
1 hr. BS > 160 mg/dl
2 hr. BS > 120 mg/dl
52

53. Serum chemistry(frequently used):
Oral Glucose Tolerance Test:
Wilkerson Point System:
A score of 2 or more indicates diabetes
FBS > 110 mg/dl - 1 Point
1 hour > 170 mg/dl – 0.5 point
2 hour > 120 mg/dl – 0.5 point
3 hour > 110 mg/dl – 1 point
53

54. Serum chemistry(frequently used):
Oral Glucose Tolerance Test:
University Group Diabetes Program Criteria:
Based on the sum of 1,2 and 3 hr. levels of Blood sugar
If sum >/= 500 mg/dl a diagnosis of diabetes is made
54

55. Serum chemistry(frequently used):
3. Glycated Haemoglobin(HbA1c):
Hb becomes Glycated by ketoamine reactions between glucose and other
sugars.
Once Hb is Glycated, it remains that way for a prolonged period(2-3
months)
Hence it provides a definitive value of blood sugar control of 2-3 month
duration
The HbA1c fraction is abnormally elevated in diabetic patients with
chronic hyperglycaemia
It is considered to be a better indicator for diabetic control compared to
blood glucose levels
55

56. Serum chemistry(frequently used):
Glycated Haemoglobin(HbA1c):
Range:
56

57. Serum chemistry(infrequently used):
1. Serum Calcium, Phosphorus:
 Indicated on suspicion of Paget’s disease, fibrous dysplasia, primary and
secondary hyperparathyroidism, osteoporosis, multiple myeloma or
osteosarcoma
 The concn. Of Serum Ca varies inversely with serum P
 Normal level Serum Ca – 9.2-11 mg/dl
 Normal level Serum P – 3- 4.5 mg/dl
 At levels less than 7 mg/dl Serum Ca, signs of tetany may appear
57

58. Serum chemistry(infrequently used):
2. Serum Alkaline Phosphatase: (ALP)
 ALP produced in small amounts in the liver but most notably in
osteoblasts
 Normal values:
ADULT CHILD
King Armstrong Units 4-13 15-30
Bodansky Units 1.5-4.5 5-14
International Units
(IU/l)
30-85
58

59. Serum chemistry(infrequently used):
2. Serum Alkaline Phosphatase: (ALP)
High values Low values
Obstructive liver disease Hypophosphatasia
Paget’s disease of bone Hypothyroidism
Osteomalacia Osteoporosis
Rickets Aplastic/Pernicious
anaemia
Sarcoidosis Chronic Myeloid
Leukaemia
Lymphoma Wilson’s Disease
59

60. Serum chemistry(infrequently used):
2. Serum Alkaline Phosphatase: (ALP)
 This test is very useful for diagnosing biliary obstruction.
 Even in mild cases of obstructive disease, this enzyme is elevated.
 It is not very useful for diagnosing cirrhosis.
 If a patient has bone disease, this test may be highly inaccurate, as ALP is
also found in bone tissue.
60

61. Serum chemistry(infrequently used):
3. Serum Uric Acid:
 End product of purine metabolism
 Normal values:
 Males : 2.1-7.8 mg/100ml
 Females : 2.0-6.4 mg/100ml
 Abnormally high uric acid level seen in Gout, Renal failure, leukaemia,
lymphoma, starvation , lead poisoning & cancer chemotherapy
 Low values are rare
61

62. Serum chemistry(infrequently used):
4. Serum Creatinine:
 Metabolic product of dephosphorylation of creatinine phosphate
 Raised in late stage Renal disease
 Its analysis is preferred to Serum Urea analysis as dietary protein intake
and protein catabolism do not alter its levels in the body
 Levels > 15 mg/dL indicates impaired renal metabolism
62

63. Serum chemistry(infrequently used):
5. Blood Urea Nitrogen:
 Formed by the deamination of amino acids in the liver
 Protein metabolism produces ammonia, a toxic substance that is
converted into urea.
 Normal values – 8 -18 mg/100ml
 High BUN readings are seen in acute or chronic renal failure, congestive
heart failure and urinary tract obstructions
63

64. Serum chemistry(infrequently used):
6. Total Protein & Albumin/Globulin Ratio:
 These proteins are important in coagulation, transport a variety of
hormones, act as buffer systems and help maintain osmotic pressure
 Normal range:
 Total protein – 6 – 8.3 g/dL
 A/G ratio - 1.2 – 2.0
64

65. Serum chemistry(infrequently used):
6. Total Protein & Albumin/Globulin Ratio:
High Total Protein values Low Total Protein Values
Lupus erythematosus Inadequate Protein Intake
Collagen diseases Protein Malabsorption
Acute liver diseases Diarrhoea
Multiple Myeloma Anaemia & Burns
65

66. Serum chemistry(infrequently used):
7. Serum Bilirubin: (Brb)
 Bilirubin is a bile pigment derived from the breakdown of Haemoglobin
 Normal value: 0.1 – 1.2 mg/100ml
 Levels beyond 3.0 mg/100ml may indicate jaundice
 High values may also indicate haemolytic anaemia, biliary obstruction,
hepatitis and Gilbert’s disease
66

67. Serum chemistry(infrequently used):
8. LDH,SGOT,SGPT:
 LDH is responsible for the oxidation of lactic acid to pyruvic acid
 Normal range: 71-207 IU/L
 SGOT(AST) is responsible for conversion of amino acids to keto acids
 Normal range: 0-35 IU/L
 SGPT(ALT) is responsible for diagnosis of liver functions more so than
SGOT levels
 Normal range: 0-35 IU/L
67

68. Serum chemistry(infrequently used):
8. LDH,SGOT,SGPT:
 These enzymes can be indicative of liver disease.
 However, these enzymes are also found in other body tissues such as
bone, heart, kidney, etc.
 Isoenzyme tests usually must be performed in order to isolate the
isoenzyme that is elevated and if the source is the liver.
68

69. Serum chemistry(infrequently used):
9. Blood Electrolytes:
 An automated analysis usually includes Sodium(Na), Potassium(K),
chloride(Cl) and Bicarbonates(HCO3
- )
 Normal values:
Sodium 136-145 mEq/L
Potassium 3.8-5.5 mEq/L
Chloride 95-105 mEq/L
Bicarbonates 22-28 mEq/L
69

70. Serum chemistry(infrequently used):
10. Serum Protein Electrophoresis:
 By this technique albumin and fibrinogen may be separated from
globulin, with globulins further separated into 4 major groups:
I. Alpha-1
II. Alpha-2
III. Beta
IV. Gamma
70

71. Serum chemistry(infrequently used):
10. Serum Protein Electrophoresis:
 In dental practice it is recommended that this procedure be carried out
I. To rule out the presence of multiple myeloma
II. Patients with radiolucent defects detected in radiographic examination of
cranium and jaws(esp. when pulpal or periodontal foci cannot be
evidenced)
III. Patients with atypical facial neuralgia
71

72. Saliva Chemistry(infrequently done):
 Secretions are collected directly from individual parotid and submandibular &
sublingual glands by use of small rubber cups(Curby cups) pressed lightly
against gland orifices
 Salivary function studies include:
1. Measurement of Na, K, Cl concentration in saliva
2. Measurement of total salivary flow
3. Rate of flow of saliva from orifices
4. Rate of discharge of radio-opaque dye from salivary gland following retrograde
sialography
5. Rate of uptake and secretion of 99m Tc-pertechnate by salivary glands
72

73. Saliva Chemistry:
 Normal values for unstimulated saliva are
 K – 25 mEq/L
 Na - <10 mEq/L
 Cl - 15-18 mEq/L
 Increase in K or Na values may indicate generic inflammation or
sialodenosis
 In parotid enlargement accompanying cirrhosis
 Parotid flow rate and salivary concn of Na,K,Cl, salivary amylase & protein
increases
 Immunoglobulin levels remain normal
73

74. Saliva Chemistry:
 In Sjogren’s Syndrome
 Flow rate is reduced
 Salivary phosphate concn is reduced
 Na & Cl concn is elevated
 Salivary IgA concn elevated
 Urea and K concn unchanged
 Abnormal protein bands can be distinguished by electrophoresis
74

75. 75

76. Microbiology: 76

77. Microbiology:
 Culture and sensitivity tests are used to isolate and identify causative micro
organisms of an infection
 May be obtained from blood or urine
 Particularly helpful in evaluating infections related to throat, sinuses, root
canals or bone.
 Sensitivity tests may also be ordered when patient relapses, the
identification of the organism is uncertain or the disease is severe
 Most common limitation is the delay in receiving the report
 Another problem is in-vitro testing may not necessarily predict the same
result as in-vivo testing
77

78. 78

79. Immunology: 79

80. Immunofluorescence Procedure:
 This procedure employs the use of fluorescent labelled antibodies to
detect specific Ag-Ab reaction of known specificity in tissue sections
 When tissue sections labelled in this fashion are illuminated with ultra
violet light in an UV microscope, specific labelled tissue component can
be identified by their bright apple green fluorescence against a dark
background
80

81. Immunofluorescence Procedure:
Direct
Immunofluorescence
• Addition of fluorescent
labelled Ab to patient
tissue
• Wash
• Visualizing under
fluorescent microscope
Indirect
Immunofluorescence
• Addition of patient
serum to tissue
containing known Ag
• Wash
• Add fluorescent
labelled Anti globulin
• Wash
• Visualize
Sandwich Technique
• Refers to the fact that
the Ag is sandwiched
between 2 layers of Ab
only one of which is
labelled
• Incubation and washing
• Labelled antiserum is
applied to the section
which identifies
location of tissue
component
81

82. Immunofluorescence Procedure: 82

83. Immunology(Infrequently used
methods):
1. ImmunoPrecipitation Assays:
 Detects Antibody in solution
 End point is visual flocculation of the antigen and the antibody in
suspension
2. Complement Fixation:
 Based on activation/fixation of complement following binding of
complement factors to Ag-Ab immune complexes
83

84. Immunology(Infrequently used
methods):
3. Particle Agglutination:
 Relatively simple and fast
 Capable of detecting lower concentration of antibodies
 Designed to detect antibodies to viruses, subsequent to vaccination
 Utilizes Ag coated latex particles, coal particles
84

85. Immunology(Infrequently used
methods):
4. Enzyme Immuno Assay:
 Most sensitive
 Usually indirect assay that depends on the use of anti human IgG or IgM Ab
conjugate
 Antibody conjugate, if present is made to attach to enzyme which catalyses
conversion of substrate to a coloured product which is then read by a
spectrophotometer
85

86. Immunology(Infrequently used
methods):
5. Radio Immuno Assay:
 Extremely sensitive and specific procedure
 Used to measure concentration of Ag in patient’s sera by using Ab
 To perform this, a known quantity of Ag is made Radioactive and is made
to compete with Ag in patient’s sera for Ab binding sites
 The radioactivity of free Ag remaining is measured using a Gamma
counter
86

87. Histopathology and Cytopathology: 87

88. Histopathology and Cytopathology:
 Histopathology refers to the microscopic
examination of tissue in order to study the
manifestations of the disease
 Cytopathology refers to the scientific study of role
of individual cells or cell types in disease
88

89. Tissue Biopsy:
 A biopsy is a controlled & deliberate removal of tissue from a living organism for
the purpose of microscopic examination
 Relatively simple procedure producing little discomfort when compared to
exodontia or periodontal surgery
 Indications:
When signs and symptoms of an observed tissue change do not
provide enough information to make a diagnosis
When neoplasia is one of the differential diagnosis
To confirm a clinical diagnosis
89

90. Tissue Biopsy:
 Contraindications:
The systemic health of the patient may contraindicate biopsy
completely or at least cause its postponement
Site of the lesion may pose a risk to biopsy (for eg. Biopsy in richly
vascularized areas may pose a risk of haemorrhage)
Cases of clinically obvious malignant neoplasm should be referred
directly to the appropriate specialist as biopsy would delay definitive
care rather than accelerate it
90

91. Tissue Biopsy:
 Avoidance of Delay for Biopsy:
1. Rapid growth
2. Absent local factors
3. Fixed lymph node enlargement
4. Root resorption with loosening of teeth
5. History of malignancy
91

92. Tissue Biopsy:
 Uses:
1. Diagnosis
2. Grading of tumours
3. Metastatic lesions
4. Recurrence
5. Management Assessment
92

93. Tissue Biopsy Types:
Excisional
biopsy:
Total excision of a
small lesion for
microscopic exam.
Diagnostic +
Therapeutic
Incisional
Biopsy
Performed by
removing a wedge
shaped specimen of
pathological tissue
along with
surrounding normal
zone
Punch Biopsy:
With this technique
the surgical defect
produced is small
and does not
require suturing
Tissue is removed in
same manner as
incisional/excisional
93

94. Tissue Biopsy Interpretation:
 The biopsy report communicates the pathologist’s opinions concerning the specimen
to the practitioner
 The format includes:
Patient summary
Gross description of the specimen
Microscopic description of the specimen
The diagnosis
Additional comments
94

95. Tissue Biopsy Interpretation:
Patient Summary:
It restates the patient information provided by the clinician
The clinician should review this info to find out any inaccuracies that may affect
the diagnosis
The only new information is the Reference Number assigned to the specimen by
the pathologist
Any future communications with the pathologist about the case must include this
reference number
95

96. Tissue Biopsy Interpretation:
Gross and Histopathologic descriptions
Gross description includes macroscopic features like colour , general shape and
metric dimensions
Microscopic description includes the composition of the normal tissues and any
abnormal findings
It can supplement the clinician’s understanding of the pathologist’s diagnosis and
may reveal the severity of some lesions.
In addition, the microscopic description should indicate if the lesion extends to the
specimen margins, which in cases of excisional biopsy may suggest the possibility
of recurrence
96

97. Tissue Biopsy Interpretation:
Diagnosis:
This is the pathologist’s opinion of the patient’s condition based on the tissue
specimen and the clinical information provided
The anatomic location of the lesion is usually specified after the diagnosis
Comments may be occasionally added by the pathologist to clarify an unusual
or a non-specific diagnosis , suggest additional diagnostic procedures or
recommend treatment methods
97

98. Tissue Biopsy Interpretation: 98

99. Exfoliative Cytology:
 Developed by Dr. George Papanicolaou who is also known as “Father of
cytology”
 In this, the surface of the lesion is either wiped with a sponge material or
scraped to make a smear.
 The appreciation of the fact that some cancer cells are so typical that they
can be recognized individually has allowed the development of this
diagnostic technique
99

100. Exfoliative Cytology:
Advantages:
•Time saving
•Painless
•Low cost
•No anaesthesia
•Screening test
• Rapid diagnosis
Disadvantages:
• Firm tumours
• False negative
results
• Non assessment
Indications:
•Patient
preference
•Debilitated
patients
•Adjunct
•Rapid
evaluation
•Population
screening
100

101. Exfoliative Cytology:
 Interpretation:
101

102. Fine Needle Aspiration Cytology(FNAC):
 Microscopic examination of an aspirate obtained by inserting a
fine needle into a lesion
 Painless and safe procedure for rapid diagnosis
 Indications:
Salivary gland pathology
As a replacement for extensive biopsy
Suspicious lymph nodes
Recurrence
Metastatic lesion
102

103. 103

104. Clinical Scenario 1:
Patient with
generalized
periodontitis w/
multiple abscesses
Preliminary
investigations:
CBC,FBS, PPBS, RBS
Occasionally:
Glycated Hb/
OGTT
Rarely:
ELISA
104

105. Clinical Scenario 2:
Patient presents with
chronic fatigue, pallor
and paleness of
conjunctiva
Preliminary investigations:
CBC inc. Hb/Hct/Red cell indices
Absolute LC/DLC
Occasionally:
Peripheral smear/
Serum Iron/ TIBC
Rarely:
Schilling’s Test
105

106. Clinical Scenario 3:
Patient presents with
recurrent bleeding
episodes/ persistent
haemorrhage post
exodontia
Preliminary investigations:
Platelet count/ BT/PT/aPTT
Occasionally:
Bone Marrow
Biopsy
Rarely:
IHC
106

107. Clinical Scenario 4 :
Patient diagnosed with
a white lesion
Preliminary investigations:
Toluidine blue/Lugol’s Iodine/Vizilite/
CBC/Exfoliative Cytology
Definitive:
Tissue biopsy
Rarely:
IHC
107

108. Clinical Scenario 5 :
Patient presents with
burning sensation in
his mouth, provisional
dignosis is RAS Major
Preliminary investigations:
CBC(may exclude RAS)
Periodic
CBC
Lesion persistent even after
6 weeks:
Tissue biopsy
108

109. Conclusion:
 Lab investigations have become an integral component of a complete
examination of the patient
 They confirm the authenticity of our clinical impression and also
provides a prognostic knowhow post treatment
 As oral diagnosticians, we should have a thorough knowledge about
different investigations pertaining to our field of study
 We should also know how to correlate our history taking and clinical
examination so as to order for the most appropriate investigation
109

110. References:
1. Scully, Crispian ; Oral & Maxillofacial Medicine ; 2nd edition
2. Prabhu, S.R. ; Textbook of Oral Medicine ; 1st edition
3. Bricker, Langlais, Miller ; Oral Diagnosis, Oral Medicine and Treatment
Planning ; 2nd edition
4. Mitchell, Standish, Fast ; Oral Diagnosis/Oral Medicine ; 3rd edition
5. Coleman , Nelson ; Principle of Oral Diagnosis
6. www.google.com
7. http://www.nurseslearning.com/courses/nrp/labtest/course/section6
/index.htm
110

111. THANK YOU & GOOD DAY
111