1) Abdominal tuberculosis can involve many abdominal organs and sites, with the ileocaecal region being most common. Diagnosis is dependent on correct identification and drug sensitivity testing of Mycobacterium tuberculosis. 2) Various diagnostic methods are available including AFB smear, culture, molecular tests like PCR and NAAT, and antigen/antibody tests. Culture remains the gold standard but newer automated non-radiometric systems like MGIT960 can provide faster results. 3) Molecular tests like nested PCR and NAAT provide very rapid results within hours but are used as supplements to culture. IFN-γ release assays and ADA levels in ascitic fluid also provide supportive diagnostic information. Proper diagnostic method selection

1. Abdominal Tuberculosis – How Far are Our Diagnostics
Illuminating?

2. Review Article
INTRODUCTION
Abdominal tuberculosis can involve the luminal,
gastrointestinal tract, liver, spleen, lymph node, peritoneum
and the female genital tract; the most common site being
the ileocaecal region [1]. The disease may develop
secondary to primary focus elsewhere in the body usually
the lungs or it may originate within intestinal tract from
swallowed sputum or rarely ingestion of cow’s milk [2].
The management is largely dependent upon the correct
diagnosis and drug sensitivity testing for Mycobactertia.
CLINICAL SIGNS & SYMPTOMS
Symptoms
Abdominal pain, fever, weight loss, anorexia, diarrhea,
constipation,nausea orvomiting,malena,haemetemesis[1].
Signs
Abdominal tenderness, abdominal distension, ascites,
hepatomegaly, splenomegaly, abdominal mass, cervical
lymhadenopathy, supraclavicular lymhadenopathy, pulsatile
mass in aorto duodenal fistula , dysphagia and odynophagia
in esophageal tuberculosis and anemia [2-4].
MICROBIOLOGICAL DIAGNOSIS
Samples
The following patient samples can be collected
ABDOMINAL TUBERCULOSIS - HOW FAR ARE OUR DIAGNOSTICS ILLUMINATING?
ShammaArora* and Raman Sardana**
*Junior Consultant (Microbiology), ** Senior Consultant (Microbiology) & Additional Director Medical Services, Indraprastha
Apollo Hospitals, Sarita Vihar, New Delhi 110 076, India.
Correspondence to:Dr. Shamma Arora,Junior Consultant (Microbiology),Indraprastha Apollo Hospitals, Sarita Vihar,
New Delhi 110 076, India.
e-mail: shamataluja@yahoo.com
Tuberculosis can involve any part of the gastrointestinal tract from mouth to anus, the peritroneum,
pancreas and the hepatobiliary system. Gastrointestinal tuberculosis mimics many clinical conditions and
only a high degree of suspicion can help in the diagnosis otherwise there are chances of missing it leading
to high morbidity and mortality. Various methods of diagnosis are available but which one is the right test for a
particular patient needs to be ascertained. Culture remains the gold standard method of diagnosis. Fast
track cultures like MGIT/ M BactAlert 3 D can give faster results with in few days to few weeks. Molecular tests
are fastest and can be used as a supplementary test. Nested PCR can give results with in few hours.
Key words: Abdominal tuberculosis, Automated methods for culture, Nucleic acid sequence based
amplification, ELISA for tuberculosis.
depending upon the clinical condition of the patient i.e.
sputum, gastric aspirate, pus, ascitic fluid, lymphnode,
gastric biopsy, omental culture and mesenteric lymph
node. The above mentioned samples can be subjected to
staining as well as culture.
Acid Fast Bacilli (AFB) smear
AFB staining provided preliminary confirmation of
diagnosis although it can not differentiate Mycobacterium
tuberculosis from other acid fast bacilli. For a reliable
results smear requires approximately 10,000 organisms/
mL. Therefore results may be negative in early stages of
disease or when the organism load is less [5]. Staining for
acid fast bacilli is positive in less than 3% of ascitic fluids
in tubercular peritonitis [6]. Two types of acid fast stains
are commonly used – Carbolfuchsin stains (ZN stain &
Kinyon stain) and Fluorochrome stains (auromine O with
or without rhodamine). Fluorochrome attains are more
sensitive but dead mycobacteria will also give brighy
yellow colour fluorescence with this stain. This feature has
to be remembered when using acid fast smears to assess
treatment efficacy and in that case if bright yellow
coloured bacilli are seen in fluorochrome stained smears;
carbolfuchsin stain should be performed for confirmation
of acid fast bacilli [5]. Besides many laboratories would
not have fluorescent microscope.
Culture
Various culture methods range from conventional
Apollo Medicine, Vol. 7, No. 4, December 2010 294

3. Review Article
295 Apollo Medicine, Vol. 7, No. 4, December 2010
culture system i.e. LJ media to automated systems of
Bactec 9000 MB, MGIT 960, ESP Culture system, MB/
BacT Alert 3D system. Besides this some semi automated
culture systems like i.e. MGIT, SeptichekAFB, MB Redox
are also available [7]. It is known that M.tuberculosis can
occasionally be isolated in stool of persons with healthy
conditions. Therefore special decontamination techniques
and BacTec technology must be used for culture [8].
In conventional culture system a positive culture is
obtained in less than 20% of cases, and it takes 6-8 wk for
the mycobacterium colonies to appear. Singh, et al
advocated that processing of one liter of ascitic fluid may
yield up to 80% positive results [6].
Bactec 460 TB
The detection time for M.tuberculosis averages 9-14
days & it may be less than 7 days for some strains of
Mycobacteria other than M.tuberculosis but disadvantages
of system include cost of instrumentation , the inability to
observe colony morphology and detect mixed cultures;
over growth by contaminants ; need for disposal of
radioactive material and extensive use of needles [8].
Mycobacteria growth indicator tube (MGIT & MGIT
960)
MGIT system consists of round bottom glass tubes and
a fluorescent compound which is sensitive to dissolved
oxygen in the broth. The tubes are observed daily for
fluorescence under wood lamp up to 6 weeks. MGIT 960 a
non radiometric automated system that holds 960 plastic
tubes which are continuously monitored. Studies have
indicated that MGIT 960 had the shortest mean time to
detection i.e. 13.3 compared to 14.8 days for BACTEC TB
& 25.6 days for LJ media [8].
MB/ Bact Mycobacteria detection system
The system is based on continuous monitor of the
microbial generated CO2 . The mean time for detection is 16
days.Again it is a non radiometric detection of mycobacteria
eliminating the need for handling and disposal of
radioisotopes [8].
ESP culture system II
The system is based on continuous monitor of the gas
pressure due to metabolic activity of microorganisms in
culture bottle. Studies have indicated that ESP detects
positive cultures three times more frequently than BACTEC
460 system and again no need to handle radioactive waste
[8].
Molecular techniques
PCR of the mucosal biopsy specimens diagnose TB in
45 to 64 % of cases [9,10]. Studies have indicated that the
faecal PCR based on IS6110 insertion element has
sensitivity and specificity of 88% & 100% respectively.The
faecal PCR was able to detect >10 copies of M.tuberculosis.
Besides this unlike endoscopic biopsy faecal PCR is a non
invasive test [11].
Nested PCR
In this PCR there is double amplification of a fragment
of the insertion element IS6110 only present in
M.tuberculosis genome[12]. The Xpert M.tuberculosis
assay/Rifampicin assay uses three specific primers and five
molecular probes to assure high degree of specificity. For
detection of rifampicin resistance it targets the rpoB gene
and the results are available with in two to three hours.
Nucleic acid sequence based amplification (NASBA)
Three steps are involved in the use of this assay:
isolation of 23 S rRNA , amplification of RNA by the
NASBA method, and the reverse hybridization of the
amplified products on membrane strips using an automated
method. Genotype Mycobacteria Direct (GTDIR; Hain Life
Science, Nehren, Germany) is based on NASBA applied to
DNA strip technology. The assay is used for the direct
detection of M.tuberculosis and other Mycobacteria i.e.
M.avium, M.intracellulare, M.kansasii and M.malmonse
from the clinical samples [13].
Besides this there are certain assays like GenoType
MTBDRplus(GTPLUS) that allows the direct detection of
M.tuberculosis in clinical samples as well as detection of
resistance to isoniazid (kat G and inh A) and rifampicin
(rpoB) [13].
Both of GTDIR and GTPLUS showed higher
sensitivities. Besides this as both of them are RNA PCR
these can differentiate between live and killed bacilli which
DNA PCR can not. GTDIR should be used in areas with
low prevalence of tuberculosis and high incidence of
infections by non tubercular Mycobacteria while GTPLUS
should be used in areas with higher incidence of tuberculosis
so that simultaneously resistance to isoniazid & rifampicin
can be detected. Testing for Ethambutol, fluoroquinolones
and aminoglycoside resistance can also be checked [13].
Antigen detection tests
ELISAbasedonantigens85Band 85C (Ag85)complex,
a 65–kDa protein that corresponded M. tuber-culosis heat
shockprotein 65(65kDaHSP),14kDaheatshockprotein
HSP and MTB heat shock protein 71 (71 kDa HSP) can be
usedascreeningtest[14].Threetypes ofantibodyresponse
Ig M, Ig G, Ig A are available. ELISA and Soluble antigen
fluorescent antibody arenotsensitiveandnonspecific and

4. Apollo Medicine, Vol. 7, No. 4, December 2010 296
Review Article
canonlysuggestaprobablediagnosis[15].
SUPPLEMENTALTESTS
• γ – Interferon assay. The interferon – gamma assay
have been used for the diagnosis of latent
Tuberculosis and active tuberculosis. The γ -
interferon assay is a cell mediated immunity based
response to peptide antigens that stimulate
mycobacteria proteins –Early secreted antigenic
target; 6 kDa protein( ESAT- 6) & Culture filtrate
protein-10 (CFP10). The proteins are absent from all
BCG strains and from most non tubercular
mycobacteria with the exception of M.kansasii,
M.szulgai & M.marinum. Individuals infected with
M.tuberculosis complex usually have lymphocytes
and recognize these and other mycobacterial antigens.
The γ - interferon assay is more sensitive in cases
with active tuberculosis compared with tuberculin
skin test and is not affected by BCG vaccination [16].
A positive test would indicate the likelihood of
infection but would not differentiate for disease
which is so common in endemic regions like India.
• Mantoux test: The test is considered to be significant
if induration is more than 20 mm done by using PPD 5
TU. One of the major limitation is possible
occurrence of false positive results in individuals
vaccinated with BCG [16]. It is a non specific test
and has a lower value than interferon- γ assay.
However it is much cheaper than other test.
• Adenosine deaminases (ADA) levels: ADA; an
enzyme is distributed in mammalian tissue particularly
in T- lymphocytes. ADA is increased in tuberculous
ascites due to stimulation of T- cells by
mycobacterial antigens [4]. Increased levels are
found in tuberculosis. Therefore it serves as
important marker of tuberculosis. It can be raised in
various infections like infectious mononucleosis,
typhoid, Viral hepatitis, initial stages of HIVinfection
and malignant tumor. In countries with high incidence
of Tuberculosis and in high risk patients measurement
of ADA in ascitic fluid might be a useful screening
test. However in population with low prevalence of
tuberculosis and high incidence of cirrhosis ascitic
fluid ADA is poor in sensitivity as well as specificity
[17-19]. Studies have indicated that in peritoneal
tuberculosis ADA estimation has a sensitivity of
100%, specificity of 96%, positive predictive value of
91.6 %, negative predictive value of 100% [20].
• ESR: The ESR varies from 0-15 mm in first hour in
males and 0-20 mm in first hour in females. The ESR
is elevated in 90 % of cases [21].
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