Association between ppd and quantiferon gold tb test in tb infection and disease among hiv infected individuals in southern iran

Abstract EN

Background : tuberculosis is one of the most common diseases among HIV-infected patients.

A person with a positive tuberculin skin test (TST) acquiring HIV infection has a 3-13% annual risk of developing active tuberculosis.

The diagnosis of TB in HIV infected patients may be difficult.

QuantiFERON-TB Gold (QFT-G) test is a novel method as an aid for diagnosis of Mycobacterium tuberculosis infection.

We evaluated the association between TST and QFT-G test in latent TB infection (LTBI) and TB in HIV-infected patients.

Methods : one hundred and seventy six HIV-infected subjects from Shiraz Consultation and Behavioral Modification Center (SCBMC) entered our study.

The individuals were screened for TST, using 5TU purified protein derivative (PPD).

Also, blood sample was provided for QFT, measuring INF-γ response to M.

tuberculosis antigen.

Results : of 176 participants, 98.3 % returned for evaluation of TST results.

Among them, 63% and 37% were negative and positive for TST, respectively.

All the participants returned for QFT-G sampling.

Of them, 64.8% and 27.8% were respectively negative and positive for the test and 7.4% showed undetermined results.

The agreement between PPD and QFT-G in their negative results was 39.9% and 8.1% in their positive results and the overall agreement was 50%.

Disagreement of TST- / QFT + was noticed in 19.7% of the subjects and TST+ / QFT- disagreement in 24.9%.

CD4+ count < 100 mm3 was seen in 5.9%, ≥ 100 and < 200 mm3 in 17.1% and CD4+ T cell count ≥ 200 mm3 in 76.9 % of subjects.

Conclusion : as the agreement rate between QFT-G and TST in HIV-infected patients was fair, a strategy of simultaneous TST and QFT-G testing would maximize the potential for LTBI diagnosis in HIV-infected subjects.