Advances in Serology for Diagnosing TB in the HIV Infected

REVIEW ARTICLE Advances in Serology for Diagnosing TB in the HIV Infected Ajay Wanchu Department of Internal Medicine, Postgraduate Institute of Medi...
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REVIEW ARTICLE

Advances in Serology for Diagnosing TB in the HIV Infected Ajay Wanchu Department of Internal Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India

ABSTRACT Tuberculosis (TB) affects more than half of all untreated HIV infected patients. Its diagnosis is hampered by the low yield of acid-fast bacilli on smear and culture studies. Advances in the serology for the diagnosis of TB in the HIV infected offers the possibility of an early diagnosis and hence, early initiation of antitubercular therapy. This review provides an update on the progress made in the early serological diagnosis of TB in the HIV infected subjects. Key words: TB, HIV, Diagnosis, Assays, Serology, Reactivation, ELISA.

[Indian J Chest Dis Allied Sci 2005; 47: 31-37]

It is over two decades since the first cases of full-blown acquired immunodeficiency syndrome (AIDS) were identified and currently human immunodeficiency virus (HIV) infection has assumed the magnitude of an international pandemic 1,2 . The notability of the global pandemic has been most striking in Asia 3. It is believed that nearly 90% of all HIV infected people are living in developing countries1. The major impact of HIV infection is in the reemergence of tuberculosis (TB) in the infected patients. Worldwide, TB is the most common opportunistic infection that occurs in the HIV infected. One summary of estimates of dual infection incidence based upon the results of 12 studies showed that the rate of TB development is 5% to 10% per year as compared to an estimated lifetime risk of 10% in those without HIV infection 4 . Incidence studies based on outbreaks with known cases in defined settings

suggest that infection and disease rates in HIVpositive individuals can be very high and that the incubation period can be very short5-7. Every year, approximately two million persons in India develop tuberculosis (TB), accounting for one fourth of the world’s new TB cases8. The estimated relative risk for TB in patients with full-blown AIDS and HIV infection compared with persons with no known risk factor is 170 and 113, respectively9. Studies from India have shown a much higher prevalence of TB in HIV infected patients as compared to the West. In a study from Madras, out of 127 HIV seropositive persons screened radiologically and bacteriologically, 59.1% had a radiographic suspicion of tuberculosis and 47.2% were positive by culture for tuberculosis10. Another study showed that among 1430 radiographically and/or bacteriologically confirmed pulmonary TB cases, HIV seropositivity rose significantly from

[Received: August 21, 2003; accepted after revision: April 2, 2004] Correspondence and reprint request: Dr Ajay Wanchu, Department of Internal Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh-160 012, India; Fax: 91-172-2744401; E-mail: .

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Serological Diagnosis of TB in HIV Infection

0.77% in 1991 to 3.4% in 199311. On the flip side, increasing prevalence of HIV in India represents a serious threat to TB control efforts. At the present rate of HIV infection prevalence in India (200 cells/ µL) the radiographic pattern tends to be one of reactivation disease with upper lobe infiltrates, with or without cavities 14. In HIV-infected persons with greater immunosuppression (e.g., CDT cell count

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