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CORRESPONDENCE
Year : 2004  |  Volume : 22  |  Issue : 2  |  Page : 131-132
 

Efficacy of immunochromatographic techniques for the serodiagnosis of tuberculosis


Tulip Diagnostics Private Limited, Bambolim Complex, Goa - 403 202, India

Correspondence Address:
Tulip Diagnostics Private Limited, Bambolim Complex, Goa - 403 202, India



How to cite this article:
Tripathi D G, Sriram N, Naik V K, Smita P, Seema A, Shakila G, Desai M W. Efficacy of immunochromatographic techniques for the serodiagnosis of tuberculosis. Indian J Med Microbiol 2004;22:131-2


How to cite this URL:
Tripathi D G, Sriram N, Naik V K, Smita P, Seema A, Shakila G, Desai M W. Efficacy of immunochromatographic techniques for the serodiagnosis of tuberculosis. Indian J Med Microbiol [serial online] 2004 [cited 2019 Dec 12];22:131-2. Available from: http://www.ijmm.org/text.asp?2004/22/2/131/8090


Dear Editor,
Tuberculosis has been declared a global emergency. The mainstay for its control and treatment is the rapid and accurate identification of infected individuals. The simplest rapid method is the detection of acid fast bacilli by microscopy. However, 40-60% of patients with pulmonary disease and ~75% of patients with extrapulmonary disease are smear negative, and in this situation even contemporary culture methods take several weeks to become positive.[1] Therefore, a number of alternative diagnostic tests have been developed. Studies carried out on 244 samples at TRC, Chennai revealed that the success rate in identification of pulmonary tuberculosis (PTB) is approximately 85% when best of the personnel and best of the techniques are employed.[2],[3] However, routine laboratories and even most of the Government hospital laboratories do not have required setup. Under such circumstances we undertook to validate newly introduced immunochromatographic test procedure for the diagnosis of PTB.
Serum samples were obtained from 173 adult subjects (> 15 years of ages, comprising of 96 patients from a tuberculosis group and 77 from a non-tuberculosis group). All the subjects were prospectively and consecutively enlisted from and among the patients presenting at chest disease TB Hospital, Taleigao, Goa and the random normal population during four month period between 16th July 2003 and 18th October 2003.
The tuberculosis group consisted of 96 patients with active tuberculosis. The inclusion criteria required atleast one of the following: (1) positive sputum acid fast smear, (2) histologic proof from tissue biopsy, and (3) suggestive chest roentgenographic findings with marked improvement after anti-tuberculosis treatment.[4]
The non-tuberculosis group consisted of 77 healthy controls and patients with chest problems other than tuberculosis. The diseases included bacterial pneumonia, chronic obstructive pulmonary disease, bronchial asthma and lung cancer. All the 173 samples were tested on the Zephyr's Serocheck MTB rapid test device without prior knowledge of the clinical status in every case by the user. Fresh serum samples i.e., within 3-4 hours of collection of blood were used in the study.
Rapid Test for TB test utilizes the principle of Immunochromatography, a unique two site immunoassay on a membrane. As the test sample flows through the membrane assembly of the device, the colored recombinant TB Ag-colloidal gold conjugate complexes with the antibodies towards TB in the sample. This complex moves further on the membrane to the test region where it is immobilized by the recombinant TB antigens coated on the membrane leading to formation of a colored band which confirms a positive test results. Absence of this colored band in the test region indicates a negative test result. Unreacted conjugate and unbound complex, if any, moves further on the membrane and are subsequently immobilized by the anti-rabbit antibodies coated on the membrane at the control region, forming a pink coloured band. This control band serves to validate the test results. The test should be considered invalid if the reference and the control band do not appear.
The overall sensitivity of Serocheck MTB rapid test was 70.83%. The specificity of Serocheck MTB was 92.20% and the overall efficiency of the Zephyr's Serocheck MTB test was 80.34%. Serocheck MTB is a reproducible and convenient rapid test for the serodiagnosis of MTB infections.
The sensitivity and specificity of the test compares favourably with existing serological tests ICT-1 and ICT-2 as reported in the published literature.[5] It is also comparable to other laboratory methods such as culture and AFB smears used for the diagnosis of pulmonary tuberculosis. Since the test does not require skilled personnel and, equipment and results can be accomplished rapidly within 20 minutes, it has an edge over existing methods for the serological screening of Mycobacterium tuberculosis infections.
We believe that availability of a rapid test for the serodiagnosis of MTB infections such as Serocheck MTB would be of great value for the diagnosis of pulmonary tuberculosis infections as a field test; as a test for routine screening and as an adjunct to clinical evaluation with existing laboratory methods.

 ~ Acknowledgement Top

We are thankful to the staff of TB and Chest Disease Hospital for their cooperation extended throughout this project. 

 ~ References Top

1.Pottumarthy S, Wells VC, Morris AJ. A comparison of seven tests for serological diagnosis of tuberculosis. J Clin Microbiol 2000;38:2227-2231.  Back to cited text no. 1    
2.Selvakumar N, Gomathi M, Rehman F, Narayanan PR. Evaluation of a two-reagent cold staining method for detection of acid fast bacilli. Int J Tuberc Lung Dis 2002;6(8): 728-731.  Back to cited text no. 2    
3.Toman K. Tuberculosis case finding and chemotherapy; World Health Organization Geneva 1979:14-22.  Back to cited text no. 3    
4.ChiangIH, Suo J, Bai KJ, Lin TP, Luh Kt, Yu CJ, Yang PC. Serodiagnosis of Tuberculosis. Am J Respir Crit Care Med 1995;156(3):906-911.  Back to cited text no. 4    
5.Gounder C, Mello FCQ, Conde MB, Bishai WR, Kritski AL, Chaisson RE, Dorman SE. Field evaluation of a rapid immunochromatographic test for tuberculosis. J Clin Microbiol 2002;40:1989-1993.  Back to cited text no. 5    
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2004 - Indian Journal of Medical Microbiology
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