FACULTAD DE MEDICINA HUMANA
GROUP N° 3
IMPORTANCEOF BIOCHEMISTRYIN MEDICALDIAGNOSTIC
ARANCIBIA CASTRO KRUZKERRY
DIAS GUEVARA EDUARDO
LOZANO BURGA YENNY
PEDEMONTE MURILLO ELKI
ROQUE VEGA KARIN
VENCES MIJAHUNCA MIGUEL ANGEL
Lambayeque, Octubre del 2011
Biochemistry, is the study of chemical processes in living organisms, governs all living
organisms and living processes. By controlling information flow through biochemical
signalling and the flow of chemical energy through metabolism, biochemical processes
give rise to the incredible complexity of life. Much of biochemistry deals with the
structures and functions of cellular components such as proteins, carbohydrates, lipids,
nucleic acids and other biomolecules although increasingly processes rather than
individual molecules are the main focus . Today the main focus of pure biochemistry is in
understanding how biological molecules give rise to the processes that occur within living
cells which in turn relates greatly to the study and understanding of whole organisms.
As an experimental science of biochemistry requires numerous instrumental techniques that
enable the development andexpansion,some of them are useddailyin any laboratory and others
are very exclusive.
o Subcellular fractionation, including multiple techniques
o Radioisotope Techniques
o Flow cytometry
o Electron Microscope
o X-ray Crystallography
o Nuclear Magnetic Resonance
o Mass Spectrometry
The most known is the use of radioiodine (Iodine-131) in the treatment of hyperthyroidism and
differentiated thyroid cancer. It is based on the emission Iodine-131 beta, high energy, short
range, which, when incorporated into the thyroid cell, produces its destruction without much
Is a technique that uses specific antibodies to a protein to remove these proteins from the
solution. The complexesof the antibody-proteinprecipitate outof solutionwith the additionof an
insolubleformof the antibody bindingproteins.Examples include protein A, protein G, Zysorbin,
Immunoprecipitin, or adding a second antibody to the solution.
In medicine,diagnosisorclinical propaedeuticisthe procedure bywhich a disease is identified or
any condition of health-disease.
The medical diagnosisisbasedsymptoms,signsandfindingsof additional teststodetermine what
disease a person suffers.
Physical experiences are reported by the patient. Not be observed.
The sings are findings in the patient and are detected by the doctor. Can be seen
o Physical Examination
It consists of various maneuvers performed by the doctor in the patient.
Inspection: is the method of physical examination is done by sight.
Palpation: isthe processof examiningthe body using the sense of touch. Provides
information on shape, size, texture, surface moisture, tenderness and mobility.
Percussion: Percussion is a method that is tapped certain body parts during a
physical examination with fingers, hands or small instruments to assess the size,
consistency, borders and presence or absence of fluid in the body's organs.
Auscultation: is to listen, either directly or through instruments like the
stethoscope, normal or pathological sounds produced by the human body.
o Supplementary Examinations
Theyare a set of studiesthatprovide valuable informationto medical analysis, and
eithertoconfirm or give more certainty tothe diagnosisof a disease.
Biopsy:procedure inwhichtissue samplesunderamicroscope toobserve.
Diagnosis and Treatment of
Tuberculous Pleural Effusion in 2006
Tuberculous (TB) pleural effusion occurs in approximately 5% of patients with
Mycobacterium tuberculosis infection. The HIV pandemic has been associated
with a doubling of the incidence
of extrapulmonaryTB,whichhasresultedinincreased recognition of TB pleural
effusions even in developed nations.
The diagnosis can be established in a majority of patients from
the clinical features,pleural fluidexamination,includingcytology, biochemistry,
and bacteriology, and pleural biopsy. The definitive diagnosis of TB pleural
effusions depends on the demonstration of acid-fast bacilli in the sputum,
pleural fluid, or pleural biopsy specimens.
The treatment of TB pleural effusions in patients
with HIV/AIDS is essentially similar to that in HIV-negative patients.
Is a leading cause worldwide of preventable morbidity and mortality from an infectious agent.
A total of nine millionnew casesandapproximately two
milliondeathsfromTBwere reported in 2004. Although
the African region has the highest estimated incidence
(356 per 100,000 population per year), the majority of
patients with TB live in the most populous countries of
the Asian subcontinent, which accounts for nearly half
of the newcasesthat arise yearly. TB pleural effusion is
the second most common form of EPTB, only less
frequent than lymph node TB.
The incidence of TB pleural effusionsinHIV/AIDShasbeen
variablyreportedfrom15 to 90%,8,9 withan effusionbeingmore common in patients with
higher CD4_ counts.
TB pleural effusionscanmanifestasprimaryorreactivateddisease.Rupture of a subpleural
caseousfocusin the lung into the pleural space is
consideredthe initial eventinthe pathogenesis of
primaryTB pleural effusions.1The accumulationof
fluidin pleural cavity results predominantly from
increased capillary permeability and secondarily
from impairment of lymphatic clearance of
proteinsandfluidfromthe pleural space because
of occlusion of pleural stomata. In contrast,
reactivationdiseaseis frequently associated with
The delayed hypersensitivity reaction responsible for the pathogenesis of TB pleural
effusionsismediatedbyT-helper type 1 (Th1) cells that activate macrophages to switch on
mechanisms responsible for the killing of mycobacteria. Clinical Features
In contrast to pulmonary TB, most TB pleural effusions manifest as an acute illness, with
approximately one third of patients being symptomatic for 1 week and two thirds for 1
month. The most common presenting symptoms are pleuritic chest pain (75%) and
nonproductive cough (70%).
Therefore,pleural tuberculosis should be considered in any adult or elderly patient with a
unilateral pleural effusion.TBpleural effusions,typicallyunilateral andsmall tomoderate in
size, usually occupy less than two thirds of a hemithorax.
The definitive diagnosis of TB pleural effusions depends on the demonstration of M
tuberculosis in sputum, pleural fluid, or pleural biopsy specimens. Supportive evidence
includes demonstration of classical TB granulomas in the pleura and elevated adenosine
deaminase (ADA) and IFN-_ levels in pleural fluid.
o Sputum Examination
Traditional dogma has stated that patients with
pleural TBwithoutconcomitant pulmonary disease
are sputumnegative and,therefore,noncontagious.
However, one study reported a remarkably high
yield of mycobacterial culture (52%) in a single
specimen of induced sputum with sputum smear
positivity in 12% of cases.
o Tuberculin Skin Test
A positive tuberculinskintestresult is supportive
evidence in the diagnosis of TB pleural effusions
in areas of low prevalence (or no vaccination);
however, a negative tuberculin skin test result
may occur inapproximatelyone thirdof patients.
A negative test result could result from the
(1) Anergy secondary to immunosuppression or
(2) Recent infection.
(3) Circulating mononuclear cells suppressing the specifically sensitized circulating T-
lymphocytes in the peripheral blood.
(4) Sequestration of purified protein derivative-reactive T-lymphocyte in pleural space.
However,resultsof atuberculinskintestrepeated6to 8 weekslater will almost always be
Pleural Fluid Examination
A TB pleural effusion is typically clear and
straw colored; however, it can be turbid or
serosanguinous but is virtually never
grossly bloody. The effusion is virtually
always an exudate.14 Pleural fluid pH is
usually between 7.30 and 7.40 (rarely ever
although it can be _ 7.30 in approximately
20% of cases.32 Pleural fluid glucose
concentration is _ 60 mg/dL in 80 to 85% of
cases.22 Pleural fluid glucose is _ 30 mg/dL
inapproximately15%of cases. Although in
the initial stage of illness(uptofirst 2 weeks),
the differential cell count may reveal predominantly neutrophils,18 serial thoracenteses
show a shift toward lymphocyte predominance.9 The older
literature suggestedthat _ 5% mesothelial cellsinpleural fluidwere rarely compatible with
TB pleural effusions.
Pleural Fluid Smear and Culture
Direct examination of pleural fluid by Zeihl- Neelsen
staining requires bacillary densities of 10,000/mL and,
therefore,detectsacid-fast bacilli (AFB) in 10% of cases.
However, in patients with HIV coinfection, the yield of
pleural fluid microscopy is 20%. Culture requires a
minimum of 10 to 100 viable bacilli and, therefore, is
more sensitive with a yield ranging from 12 to 70%, with
the majority of series showing diagnostic yields of 30%.
Sensitivityof mycobacterial culture canbe improvedbybedside inoculation of pleural fluid
and by using liquid culture media or BACTEC system.
ADA (adenosine deaminase)
ADA is an enzyme inthe purine salvage pathwaythatcatalyzesthe conversionof adenosine
and deoxyadenosine to inosine and deoxyinosine with the release of ammonia. Although
ubiquitousindistribution,itplaysanimportantrole indifferentiation of lymphoid cells and
is most abundant in lymphocytes (predominantly active T-lymphocytes) whose
concentration is inversely related to the degree of differentiation.
Pirasand colleaguesforthe firsttime in1978 reportedhighlevelsof ADA inpatientswithTB
pleural effusions.Subsequently,several studieshave exploredthe usefulness of estimation
of ADA activityinthe diagnosisof TBpleural effusions.Itwasdeterminedthatapleural fluid
ADA level 70 IU/L is highly suggestive of TB, while a level 40 IU/L virtually excludes the
A metaanalysis of 40 studies published from 1966 to 1999 concluded that the test
performance of ADA (sensitivity range 47 to 100%, and specificity range 0% to 100%) in
diagnosing TB pleural effusions is reasonably good (adequate to avoid pleural biopsy in
young patients from areas with high prevalence of TB).
Produced by T-lymphocytes, is capable of activating macrophages, increasing their
bactericidal capacityagainst Mtuberculosis andis involvedingranulomaformation. Several
studieshave foundelevatedconcentrations of INF in TB pleural effusions, which is related
to increased production at the disease site by effector T cells.
Other diseases that can cause elevated INF levels in pleural fluid include hematologic
malignanciesandempyema.Immunosuppressedpatients(HIV orafterrenal transplant) had
INFlevelssimilartoimmunocompetentindividualsretainingitsefficacy as a diagnostic test.
Polymerase chainreaction(PCR)isbasedonamplificationof mycobacterial DNA fragments.
As TB pleural effusionis paucibacillarydisease,the sensitivitycould be improved by PCR, as
it can detect as few as 10 mycobacteria. Advantages of PCR include rapid diagnosis,
improved specificity and sensitivity, and no requirement of intact immunity.
Numerousstudies(Table)evaluatingthe efficacyof PCRfordiagnosisof pleural tuberculosis
have shown a sensitivity ranging from 20 to 90% and specificity from 78 to 100%.
o Other diagnostictests
The utilization of immunodiagnostics is hindered by its low sensitivity. The table lists the
detailsregarding various studies using immunologic markers in the diagnosis of tb pleural
effusions. Further studies are required to address the clinical utility of these markers.
Cytokine-producing cells and various cytokines have been demonstrated in pleural fluid
frompatientswithTB pleural effusions. The emerging role of IFN has been discussed (vide
Significantly higher levels of IL-6 have been demonstrated in TB effusions compared to
parapneumonic and malignant pleural effusions.
The natural history of an untreated tuberculous pleural effusion is characterized by
spontaneous resolution in 4 to 16 weeks with subsequent development of active
pulmonary TB or EPTB in 43 to 65% of cases over the next several years. These data
emphasize the importance of proper diagnosis and treatment of tuberculous pleural
effusions.Accordingtothe directlyobservedtreatmentshortcourseguidelines, severely
ill patientswithextensive or bilateral pleural effusions and sputum positivity are given
treatment under category I (treated during intensive phase with four drugs: isoniazid,
rifampin,pyrazinamide,andethambutol for2 monthsfollowedbycontinuationphase of
4 monthswithisoniazidandrifampin).Those withasolitaryTBpleural effusionshouldbe
treatedwithisoniazid,rifampin,andpyrazinamidefor2 monthsfollowedby 4 months of
twodrugs, isoniazidandrifampin.Especially in loculated TB pleural effusions, there can
be delayedresorption of pleural fluid even after completion of 6 months of treatment.
A hypersensitivity reaction to M tuberculosis results in granulomatous pleuritis.
Corticosteroids through their antiinflammatory action may hasten fluid resorption and
preventpleural adhesionsduringhealing.Threerandomizedtrialshave investigated the
possible role of adjunctive oral corticosteroidsin TB pleural effusion. A dose of 0.75 to 1
mg/kg/d was used for a period ranging from 4 to 12 weeks. Early resolution of clinical
symptoms and signs including fever, chest pain, and dyspnea was observed. Although
there wasa trendtowardlessresidual pleural fluidatthe endof treatment,there wasno
difference inthe developmentof residual pleural thickening or adhesions on follow-up.
Residual lungfunctionwassimilarbetween steroid and control groups at completion of
treatment. All three studies had insufficient power to examine death as an outcome;
nevertheless, no deaths occurred in the study groups.
UNRESOLVED ISSUES AND CONCLUSIONS
There have been significant advances in the understanding of pathophysiology of TB pleural
effusions. The more frequent use of imaging modalities, such as CT, and bronchoscopic
techniques, such as BAL, has lead to detection of underlying pulmonary TB in a larger
proportionof patients.However,the implicationof these findings in the treatment of patients
withTB pleural effusionisunclear.Likewise,the estimationof ADA and IFN in pleural fluid has
gained wide acceptance in the diagnosis of TB pleural effusion. However, the use of these
investigations may be limited because of availability and quality control, especially in
developing nations. Porcel and Vives found effective prediction models to differentiate
tuberculous from malignant pleural effusions based on readily available clinical (age,
temperature, history of malignancy) and pleural fluid (RBC, protein, ADA, pleural to serum
lactate dehydrogenase ratio) data, although further validation is needed. The proper use of
corticosteroids in the treatment of TB pleural effusions remains unresolved. It is hoped that
further research to clarify these issues will result in better diagnostic and therapeutic
approaches to TB pleural effusions.