Chemical pathology involves the biochemical analysis of bodily fluids to aid in disease diagnosis and management. Dr. S.A. Sakyi's presentation outlines the scope and objectives of chemical pathology, which includes describing disease mechanisms, selecting appropriate tests, and specimen collection and handling. Key aspects covered include common tests performed in chemical pathology laboratories, the roles of chemical pathology in healthcare, and factors that can influence laboratory test results such as diet, medications, and specimen processing.

1. DR. S. A. SAKYI
Dept. of Molecular Medicine
SMS, KNUST

2. OUTLINE
• Introductiontochemicalpathology
• Specimencollection&handling
• Sideroomtesting/pointofcaretesting/near
patienttesting

3. OBJECTIVES
• Describe the biochemical and pathophysiological
mechanisms of diseases and the biochemical principles
underlying their treatment.
• Select appropriate laboratory test and interpret the
results to confirm or refute a provisional clinical
diagnosis and to monitor progress during treatment.
• To understand the potentials and limitations of various
laboratory tests.
• Collect the right type of specimens for laboratory
investigations under the right conditions.

4. CHEMICAL PATHOLOGY
Clinical Biochemistry
Clinical Chemistry
Medical Biochemistry
Pure Blood Chemistry
Physiological Chemistry

5. Chemical Pathology
The systematic study of
biochemical processes associated
with health & disease &
the measurement of constituents in
body fluids or tissues to
facilitate diagnosis of disease.

6. CHEMICAL PATHOLOGY
• Chemical Pathology is the study of the biochemical basis
of disease, and the application of biochemical and
molecular techniques in diagnosis
• Constant changes in the chemical constitution &
biochemical mechanisms of the body as a result of
disease.
• Chemical pathology is a sub-specialty within pathology
which extends across most medical specialties and
involves the chemical analysis of bodily fluids

7. SCOPE OF CLINICAL CHEMISTRY
Biochemistry
Instrumentation
Computers
Pharmacology Endocrinology
Analytical Chemistry
Toxicology
Immunology
CLINICAL CHEMISTRY

8. Add anticoagulants
(heparin, potassium
oxalate)

9. Separation of Components
Plasma = Less Dense
RBCs
More Dense
Platelets / WBCs

10. Plasma vs. serum
Plasma is the liquid,
cell-free part of
blood, that has
been treated with
anti-coagulants.
Anticoagulated
Serum is the liquid
part of blood AFTER
coagulation, therfore
devoid of clotting
factors as fibrinogen.
serum= plasma - fibrinogen
Clotted

11. Components of Plasma
Blood plasma Consists of:
Water 90%
Plasma Proteins 6-8 %
Electrolytes (Na+ & Cl-) 1%
Other components:
Nutrients (e.g. Glucose and amino acids)
Hormones (e.g. Cortisol, thyroxine)
Wastes (e.g. Urea)
Blood gases (e.g. CO2, O2)

12. CHEMICAL PATHOLOGY
Primarily involves the chemical analysis of the following
bodily fluids:
• whole blood
• serum or plasma
• urine
• cerebrospinal fluid
• Faecal material
• effusions
• seminal fluid
• sweat and amniotic fluid to assist in the diagnosis of
various disease

13. ROLE OF CHEM. PATHOLOGY IN HEALTHCARE
Diagnosis: used to help differentiate
between several possibilities based on the
initial history and examination
Monitoring: to check disease progression
or response to therapy e.g. monitoring DM
patients

14. ROLE OF CHEM PATH IN HEALTHCARE
Screening: to screen for the presence of disease
in an apparently healthy population or detection
of disease before it is clinically evident
Prognosis: providing information on disease
susceptibility e.g. cholesterol can predict the risk
of coronary artery disease.
Serves as tools to assist clinicians in the diagnosis
of various disorders, as well as management and
follow-up of patients

15. WHY CHEM PATH?
– Providing a consultation service to clinicians to advise
on the most appropriate testing within specific clinical
situations
– Interpretation of a wide variety of clinical laboratory
tests
– Advice regarding the limitations of laboratory tests in
specific circumstances
– Advice on the influence of "pre-analytical" factors,
medications and other factors on laboratory tests
which may influence clinical decision making

16. WHY CHEM PATH
– Ensuring the quality of laboratory testing through
internal and external quality assurance
– Introduction of new tests, since medicine and
clinical testing is a rapidly evolving science and
new tests are developed continuously
– Training of medical students in the appropriate
selection of clinical laboratory testing and the
most cost effective and appropriate use of the
clinical laboratory

17. • Selecting the right test, at the right time, for the right patient.
After making the decision that an investigation is necessary,
and selecting the most appropriate test,
• Consideration to factors present that may affect the
interpretation of results, or even the decision to proceed with
the test at that time

18. Analyses performed within the Chemical Pathology
laboratory include:
– Water and electrolyte balance and kidney function
– Acid base balance
– Liver function
– Minerals such as calcium, magnesium and phosphate
– Proteins and enzymes
– Lipids such as cholesterol and triglycerides and risk factors for
heart disease
– Diagnosis of diabetes mellitus and it's complications
– Cardiac markers for detection of cardiac damage
– Iron and porphyrins
– Endocrinology, including:
• Pituitary function
• Sex hormones
• Thyroid function
• Adrenal hormones

19. Analyses performed within the Chemical Pathology
laboratory include:
– Tumour markers such as Prostate specific antigen (PSA)
and various other markers used in the detection and
management of cancer patients
– Inherited metabolic diseases
– Therapeutic Drug Monitoring (TDM)
– Drugs of abuse testing
– Allergy testing
Specialised testing including:
– Occupational Health testing (monitoring of exposed
workers)
– Insurance testing
– Environmental testing (water analysis, etc.

20. VACUTAINER/EVACUATED TUBES
• These are tubes for blood collection which
are color-coded based on the anticoagulant
present. They come in various sizes; 2, 5, 7,
and 10 ml.
• Blood is drawn in this order: Blood culture
tubes, red top, blue top, green top, lavender
top and gray top

23. COLOR ADDITIVE ACTION USE
Lavender Ethylenediaminetetraacetic chelates calcium hematologic assays
Acid (EDTA) lead assay, CEA
* Versene (disodium salt) Determination and
* Sequestrene (dipotassium salt) cell counts
Red None Allows blood to clot Most chemistry,
immunologic and
blood bank tests
Red Gray or None but contains Allows blood to clot Most chemistry tests
Red Black separator material
and serves as a
barrier between cells
and serum
Yellow Citrate dextrose preserves RBCs Blood culture
Green Heparin (Na+, Li+, inhibits thrombin ammonia CO-Hb
or, NH4
+) activation and methemoglobin

24. COLOR ADDITIVE ACTION USE
Orange Thrombin accelarated clot STAT serum
tests
Blue Buffered citrate binds calcium Coagulation assays
like PT & APTT
Black Buffered sodium binds calcium Westergren ESR
citrate
Gray NaF/K2C2O4 Inhibits glycolytic Glucose
enzyme enolase and determination
act as anticoagulant
Iodoacetate inhibits glycolytic Glucose
enzyme glyceraldehyde determination
3-phosphate
dehydrogenase

25. Anticoagulant Interference
– Dilution errors especially oxalates which are
highly osmotic
– Inhibition of plasma enzyme activities activities
especially with fluoride which is an enzyme
poison, EDTA which chelates metallic enzymes
activators. Oxalate inhibits AMS, LD and ACP,
and citrate which inhibits AMS
– Oxalates, citrate and EDTA lower plasma calcium
levels
– False increase in electrolyte analyses due to the
anticoagulants in the salt form

26. If multiple tubes are needed, the proper order of draw to avoid cross
contamination and erroneous results is as follows:
1st - Blood culture vials or bottles, sterile (yellow or yellow-black top)
2nd - Coagulation tube (light blue top) NOTE: If just a routine coagulation
assay is the only test ordered, then a single light blue top tube may be
drawn. If there is a concern regarding contamination by tissue fluids or
thromboplastins, then one may draw a non-additive tube first, and then
the light blue top tube.
3rd - Non-additive tube or Serum tube
Last draw - additive tubes in this order:
1. SST (red-gray or gold top). Contains a gel separator and clot activator.
2. Sodium heparin (dark green top)
3. PST (light green top). Contains lithium heparin anticoagulant and a gel
separator.
4. EDTA (lavender top)
5. ACDA or ACDB (pale yellow top). Contains acid citrate dextrose.
6. Oxalate/fluoride (light gray top)

27. Specimen Handling and Processing
Serum
– 20-30 minutes is the ideal clotting time
– Generally more preferred than plasma
1. Interfering substances are co-precipitated
during clotting such as LPL(lipoprotein
lipase)
2. Optically clearer
3. Free from anticoagulant interference
– Must ideally reach the laboratory within 45
minutes
– Agitation must be avoided during transport
– Use amber containers for photolabile
substances
– Transport in ice (4 deg C) those specimens for

28. Specimen Interference
Lysis of cells or Laking (Hemolyzed serum)
– Results in leakage of intracellular substances
– Lysis of RBCs is called laking or hemolysis
which may occur in vivo or in vitro
– In vitro hemolysis is more common which may
be due to:
1. Use of vacuum tubes
2. Vigorous mixing
3. Use of too narrow or too wide needle bores
4. Effect of alcohol
5. Centrifugation and separation steps
– Hemolysis is visible only not until a 200 mg/L
of hemoglobin level in present

29. Icteresia (Icteric serum)
– Intensely yellow serum sample due to elevated
bilirubin value
– Jaundice in a patient is caused by a bilirubin
level of greater than 430 µM (25 mg/L)
– Bilirubin interferes with tests using dyes and
turbidity tests
– Interference due to bilirubin may be minimized
by sample blanking or dual wavelength method
known as the Allen correction method

30. Lactescence (Lipemic serum)
– Obtained normally after a meal due to
elevated chylomicrons
– Characterized by milky or highly turbid
serum
– Lactescence appears when the TAG level
reaches 4.6 mM (4g/L)
– Errors due to lipemia may be corrected
by ultracentrifugation of the serum
sample

31. Grounds for rejecting a specimen
–Inadequate sample identification
–Insufficient volume of specimen collection
–Inappropriate collection tube
–Hemolysis
–Improper transportation

32. QUALITY MANAGEMENT
Quality Assurance (QA)
– includes maneuvers encountered in the
analytic, pre-analytic and post-analytic
phases of laboratory testing
Pre-analytical phase includes:
– test ordering
– specimen collection
– transport of the specimen in the laboratory

33. Analytical phase includes
–specimen analysis (manual or automated)
–use of commercial controls
–record keeping
Post-analytical phase includes
–reporting out results of analysis (manual or
computerized)
–physician contact

34. Specimens or samples are
analyzed
while
substances in them are
measured or quantitated.

35. Substances measured in serum fall generally into
the following categories:
1. Substances normally present with a function in the
circulation
 electrolytes
 TAG, cholesterol
 hormones
 vitamins
 glucose
 TP
 albumin
 individual proteins
2. Metabolites- nonfunctioning waste products in
the process of being cleared
 urea
 creatinine
 uric acid
 ammonia
 bilirubin

36. 3. Substances released from cells as a result of
cell damage & abnormal permeability or
abnormal cellular proliferation
enzymes such as LD, ALT, AST, CK, AMS,
GGT, ALP & ACP
ferritin
4. Drugs & toxic substances
 antibodies
 substances of abuse
 therapeutic drugs
 poisons

37. FACTORS TO CONSIDER PRIOR TO SPECIMEN
COLLECTION
• Patient’s Diet: Ca, OGTT.
• Patient’s current medication:
Oral Contraceptives, Cough Mixtures
• Time of day:
Iron & Corticosteroids

38. FACTORS TO CONSIDER AT THE TIME OF
COLLECTING THE LAB SPECIMEN.
• Patient posture :proteins and protein-bound
constituents change with posture e.g. Albumin,
calcium, cholesterol, cortisol and protein bound
iodine.
• Venostasis: raise the conc. of plasma proteins,
haemoglobin, hormones, calcium & lipids. Remove
the tourniquet soon after puncturing the vein
• Site of venipuncture: eg. site of infusion-fluid is
likely not have mixed with the entire blood vol.

39. FACTORS TO CONSIDER AT THE TIME OF
COLLECTING THE LAB SPECIMEN.
• Haemolysis: release of erthrocytic content
eg. K+, Lactate dehydrogenase, acid
Phosphatase.
The plunger of the syringe should not be
drawn too fast
There should be an easy flow of blood.

40. FACTORS TO CONSIDER AT THE TIME OF
COLLECTING THE LAB SPECIMEN.
• Identification of specimen-
Patient’s name
Location/ward
Identifying number
Date
Time of specimen collection
Suspected pathology
 HIS LIS PID PTS

41. FACTORS TO CONSIDER AT THE TIME OF
COLLECTING THE LAB SPECIMEN
Specimen container:
Tubes into which the blood is expelled must
be clean.
FBS- Flouride oxalate tubes
Anticoagulant in the tube should be mixed
with the blood by gentle rotation

42. PRESERVATION OF SPECIMEN IN TRANSIT
• BloodGasAnalysis:Pco2,Po2
samplemust be kept at 4oC from the time sample
is drawn till serum or plasma is separated from
cells.
Transfer of specimen to the lab must be done by
placingthespecimeninacontainerofice.

43. PRESERVATION OF SPECIMEN IN TRANSIT
Specimen for hormonal assays e.g. gastrin,
rennin and parathyroid hormone must be
separated from the cells in a refrigerated
centrifuge.
Specimen for bilirubin and carotene must be
protectedfrombothsunlightandfluorescentlight
toavoidphotodegradation.

44. CHANGES THAT OCCUR IN THE BLOOD AFTER
COLLECTION
 Diffusion of K+ and Lactate Dehydrogenase (LDH) &
Aspartate Transaminase (AST) through the red cell
membrane into the serum/plasma.
 Decrease in conc. of glucose by erythrocytic glycolysis.-
prevented by the use of fluoride oxalate tubes.
 Loss of activity of liable enzymes such as Prostatic acid
phosphatase-protease inhibitors.
 Photo degradation of bilirubin & B-carotene by light. -
prevented by keeping the sample in aluminium foil.

45. FACTORS THAT INFLUENCE
LABORATORY TESTING
Increased Decreased
Exercise Immediate effects:
Alanine and lactate
FFA
Long-term effects
CK, LD, AST, platelets,
testosterone,
androstenedione and LH
Fasting Most analytes
(8-12 hrs for common bilirubin, FFA, TAG Glucose
metabolites and
12-14 hrs for lipid profile)
EFFECT ON LABORATORY
RESULTS

46. Increased Decreased
After eating K, TAG (chylomicrons),
ALP intestinal isoenzyme,
turbidity of serum and plasma
Diet
High meat NPNs (esp. urea, ammonia,
and urate except creatinine)
High ratio of unsaturated Serum
to saturated fat cholesterol
Purine-rich Urates
High caffeine FFA, catecholamine release
Bananas, pineapple, Serotonin in blood
tomatoes and 5’HIAA in urine
avocados
Alcohol ingestion
Immediate Lactate, urate, ketone bodies,
and FFA
Chronic abuse HDL-cholesterol, GGT, and MCV

47. Increased Decreased
Tobacco smoking
Acute effects Catecholamines, cortisol Eosinophil
neutrophils, monocytes
and FFA
Chronic effects CO-Hb, MCV and leukocyte
count
Prolonged tourniquet application Serum enzymes, protein,
protein-bound substances,
cholesterol, TAG, Ca, blood
cell concentration (hemoconcentration)**
Postural changes same as ** due to hydrostatic
efflux of water
Stress lactate, FFA and alteration
in electrolyte levels

48. Summary of Pre-analytical variables
•age, gender, race, and pregnancy
•diet, starvation, and physical activity
•caffeine, cigarettes, and alcohol
•timing of sampling
•diagnostic and therapeutic measures
•posture and tourniquet
•site of sampling
•anticoagulants
•transportation of samples
•storage, processing, centrifugation, and distribution
•effects of lipemia, hemolysis, and hyperbilirubinemia

49. Point-of-care Testing (POCT)
• Also known as near-patient testing, alternate-site
testing or patient-focused testing
• Used in emergency dept., operating suites, clinics,
health maintenance organization (HMO),
physicians, offices & nursing homes
• Addresses acute patient needs
• Instrumentation includes portable chemistry
analyzers, glucometers, BG Analyzers,
hemoglobin meters & coagulation testing

50. SIDEROOMTESTING/POINTOFCARETESTING/NEAR
PATIENTTESTING
• Refers tests performed outside the hospital
laboratory by untrained healthcare
professionals or non-laboratory personnel.
• Bedside
• Clinic
• By patients themselves at home

51. CATEGORIZATION
Simple side-room tests: qualitative or semi-
quantitative: mostly performed on urine or. eg.
urine dipsticks tests
Simple side-room test, semi-quantitative or
quantitative: mostly performed on blood
specimens. e.g. Glucometers
Quantitative tests performed with equipment
that have microprocessor-controlled operations.
can be quickly and reliably operated after little
instructions.

52. ADVANTAGES OF SRT/NPT
• Turn Around Time- Relatively short analysis
time.
• Early treatment and shorten the patient
wait .
• Ease of use– can be perform by less trained
personnel or by the patients themselves
• Prompter stabilization of life-threatening
crises (eg drug overdose)

53. ADVANTAGES OF SRT/NPT
• Closer therapeutic management (e.g. diabetes)
• Better patient compliance with therapy
(diabetes, hyperlipidaemia)
• Reduce:
– Repeat clinic/patient visits
– Length of stay in hospital
– Use of blood products (implantable biosensors)

54. DISADVANTAGES OF SRT/NPT
• Analytical performance can be inferior to
lab (eg. some glucometers)
• Risk of poor operator competence
• Risk of poor equipment maintenance
• Cost per test relatively more expensive.

55. SETTINGS FOR NPT DEVICES
ACCIDENT & EMERGENCY
Quick turnaround time for results
e.g. Diagnosis of acute MI- whole blood troponin
NPT device.
Drug overdoses- plasma p’mol, cocaine.

56. SETTINGS FOR NPT DEVICES
• DRUG ADDICTION CLINICS
measure misused drugs and alcohol(
Alcohol breath test)
screen workers for substance abuse.
Roche Diagnostics– for qualitative testing for
ethanol in either saliva or urine.

57. SETTINGS FOR NPT DEVICES
• NEONATAL CARE AND ADULT INTENSIVE CARE
Neonatal units: determination of blood
bilirubin using NPT bilirubinometers.
• PATIENT SELF-TESTING
eg. Pregnancy self-testing using over-the-
counter pregnancy test kits

58. NEAR PATIENT TESTING & DIABETES MELLITUS
NPT self monitoring is often used in the
management of diabetes mellitus.
glucose determinations in urine
ketones in urine or plasma
blood glucose measurements
urinary microalbumin tests

59. Sakyi AS, Laing EF, Ephraim RK, Asibey OF, Sadique OK. Evaluation of
analytical errors in a clinical chemistry laboratory: A 3 year experience.
Ann Med Health Sci Res 2015;5:8-12.

60. The depth of your struggle determines the
height of your success