Tuberculosis - Emerging Diagnostic Methods

TUBERCULOSIS - EMERGING DIAGNOSTICin Peru gained the success as affordable, and primary
METHODS.drug resistance can be performed with simple
Challenges Ahead.efforts, But inverted microscope is essential to read
(Role of Clinical Microbiology Laboratories)the results at frequent intervals. Contamination or
Importance of Microscopy:hazard to technical personnel is minimal. Even the
Smear examination for the detection of Acid fastdistrict laboratories can report resistance to Isoniazid
bacilli continues to be the gold standard in Diagnosisand Rifampicin In spite of several controlled studies
of Tuberculosis. In spite of several inadequacies,on MODS assay is poor to discriminate between,
Microscopy for AFB detection is economical, specificM.tuberculosis from Non Tuberculosis Mycobacterium.
and the man power can be trained easily. TheThe success of MODS is a great breakthrough in
detection of AFB in sputum smears helps for higherdetection of MDR strains provided the prevalence of
case detection, and contains the spread ofNTM prevalence is low MODS assay can identify
Tuberculosis in the Society.patients with TB in approximately on third of time
The smear will become Postive when one has bacillirequired for culturing on L J medium.
more than 5,000 - 10, 000 / 1 ml of sputum. MultipleEmerging and Rapid Diagnostic methods.-
smear examinations, at least three morning1 Fast plaque with phage amplification technology,
specimens are advised and appropriate collection oftested in areas with high rates of HIV infection, had
specimens will increase yield to > 43 %. If effortscontradicting results, needs more understanding.
were taken in educating patients for 1- 2 minutes in2. Quanti - Feron TB test - Done on Blood specimens,
methods to collect the sputum, will yield higherbased on the principle of ELISA and enzyme linked
results. Sputum induction procedures are helpful.immunospot. With higher production of Interferon
Today's emphasis to identify AFB, in smears is moreγ (Inf-γ) by cells in response to
demanding with associated HIV/AIDS, as few bacilliMycobacterium tuberculosis, than to the other
are excreted. Concentration of specimens andenvironmental Mycobacterium in particular to
digestion of thick and mucous associate specimensMycobacterium avium complex. The testing results
with Sodium hypochlorite, Sodium hydroxide, N-acetylcorrelated with Tuberculin skin test reactivity, but still
-cystine - Sodium hydroxide will increase rate ofhampered in BCG vaccinated.
detection to > 18 % in sensitivity and incremental3 Elispot - Tested by Elisa methodology detects
yield of 9 %( positve after treatment with aboveInterferon γ produced by T lymphocytes in
chemicals - positives with direct Ziehl Nelson's strainingresponse to latent Tuberculosis
) Sodium hypochlorite is beneficial in HIV positiveInfection. Elispot gained more clinical acceptability and
patients as it is Mycobactericidal and also kills humanadvantageous, being negative in majority of BCG
Immunodeficiency virus, but not suitable for culturingvaccinated individuals
specimens.Both the above testing methods were limited to high
Need for Florescent Microscopyend laboratories and cost of testing remained the
The developing world should explore themajor limitation in many developing countries. More
Fluorescence microscopy, which will improve thehelpful to diagnose the latent Tuberculosis Infections.
sensitivity of Microscopy in patient who excrete fewMolecular Technology:
bacilli as in association HIV infection, The role of ZiehlThe fast gains of Polymerase technologies by
Neelsen's method of staining and conventionalamplification of DNA (PCR) are limited to controlled
Microcopy is losing the sensitivity with ever increasingstudies interpreted in relation to clinical context and
work load, technicians opting to see few fields,performance of the laboratory .Rapidly changing
monotonous nature of work, the lack ofmolecular technologies, out dating earlier hardware,
accountability, and inter Institutional quality controlother equipment and patented primers, added to
protocols. Many systematic reviews indicated use oflimitations in the Developing world. Mainly used as
Florescent Microscopy will increase 10% higherrestricted research tool, and unaffordable to the
sensitivity and 9 % in incremental yield whenneedy poor.
compared with Z.N method of staining. About 15Many extra pulmonary tuberculosis cases were
times as many fields of view can be scanned bybenefited with Molecular technology.
Fluorescent Microscopy as by conventionalFuture Goals in Control of Tuberculosis ;
Microscopy in the same period. The developingStop TB partnership, Global Plan for 2006 to 2015 call
countries face crunch to buy Fluorescent microscopesfor strengthening of network to facilitate detect all
and to maintain the regular availability of florescentTB cases including smear negative tuberculosis. The
dyes. It is utmost important to develop centralizedEmphasis should focus on Sputum concentration
and dedicated centers for Microscopy to have controlmethods, promoting the use of Fluorescent
on peripheral laboratories. Negative smears byMicroscopy. Helping the smaller laboratories to initiate
conventional Microscopy needs further attention withculturing, and antibiotic sensitivity testing. The present
optimal microscopy, concentration methods to detectaffordable option may remain with utilizing the
AFB to reduce early mortality among the infectedmethodology of MODS .The Developing world wishes
and to contain the spread in society.to utilize this upcoming technology for practical, and
Culturing for Mycobacterial Isolationsimple way to detect the MDR tuberculosis even at
Sputum culturing remains a gold standard fordistrict Laboratories
diagnosing Mycobacterial infections. A Postive grwoth. Yet there is no fool proof, sensitive and specific
can be demonstrated with few bacilli to as low as 10test, which is inexpensive and rapid method for
- 100 of viable bacilli per I ml of sputum. CulturesDiagnosing the Tuberculosis.
show growth of AFB even when patients where onGreat challenges include detection and controlling of
treatment and negative by smear examination. AMDR TB. Strengthening the Smear Microscopy, and
simple measure with decontamination of specimensmore aggressive provisions for enforcing the
and inoculation of at least 150 - 200 µl ofFluorescent microscopy, may reduce the incidence of
concentrate on culture medium will increase thespread of tuberculosis. We have to watch the
success in culturing. In spite of best decontaminationImpact of X-MDR in the Indian continent. The
procedures, 1 - 4 % of the isolates are false Postive.undergraduate and postgraduate Medical students
The greatest limitation of culturing on Lowenstein -should be taught with more emphasis on control of
Jensen medium and other equivalent medium is longdrug resistant tuberculosis The best options with
periods (2 - 12 weeks) for isolation of bacteria.implementation of International standards for
Advances in Diagnostic Methodologies.tuberculosis care with initiation of Major global health
1. Mycobacterial growth in Incubator tube MGITparticipation may bring hope to reduce the incidence
(Mycobacterium Growth Indicator Tube) is one newof Tuberculosis by 2015.
culturing method, costlier to install and automatedArticle generated for the Medical and Paramedical
system. Economic limitations and timely availability ofstudents and Policy makers on Clinical Laboratories in
reagents (closed system committed to theDeveloping World on emerging needs in Diagnosis of
manufactures.) continue to hamper the growth ofTuberculosis.
technolology in developing world.
2.. Recent success with MODS ( the MicroscopicE mail at; tvraodoctor2000@yahoo.co.
Observation of drug susceptibility Assay ) developed