Background:  Annual tuberculin skin testing (TST) is used to diagnose latent tuberculosis infection in HIV-infected participants enrolled in the MTCT-Plus Initiative, a multinational HIV care and treatment program. There remains a question of whether high CD4⁺ count or improvement of CD4⁺ count on ART affects the positivity or conversion of TST, respectively. This study aimed to determine the risk factors of TST positivity and TST conversion in adults with HIV infection.

Methods:  The MTCT-Plus Initiative in Bangkok Thailand has enrolled HIV⁺ pregnant and postpartum women and their families since February 2002. TST is done at enrollment and then annually for all adults except those who previously treated for latent tuberculosis infection or TB disease. Symptoms checklist and chest x-ray were used to exclude TB if TST was positive (³5-mm induration).

Results:  Among 805 adults, 621 (82%) had TST at enrollment, 48 (5.9%) had previous TB, 12 (1.5%) ever received INH prophylaxis and 124 (15.4%) were no tested. Of those tested, 458 were index women and 163 (26.2% of index women) were male partners. 63.0% had concordant and 37.0% had discordant TST results. 128 (20.6%) had positive TST⁺ TB was found in 12 (1.9%) and latent tuberculosis infection was found in 116 (18.7%). Gender, age, baseline CD4⁺, ART status, pregnancy or TST result of partner were not associated with TST⁺ by univariate analysis. Size of induration was not correlated with latent tuberculosis infection vs TB diagnosis or CD4⁺.Among 167 adults who tested TST^­ at enrollment and had repeat TST at ³12 months, 124 were index women and 43 were partners; 85 (68.5%) had partners TST result at enrollment and 18 (21.2%) of these were TST⁺; 23 (13.8%) had TST⁺ at year 2 testing; all had latent tuberculosis infection. Gender, age, baseline CD4⁺, ART status, pregnancy, change of CD4⁺, or commencement of ART were not risk factors for “TST conversion” by univariate analysis. TST⁺ of partner at enrollment was associated with TST conversion at year 2 (p = 0.019). In multiple logistic regression analysis, TST result of partner remained significantly associated with TST conversion (p = 0.017, OR, 95%CI 7.3, 1.4, 37.0).

Conclusions:  TST effectively identifies tuberculosis infection in HIV⁺ adults. High rates of latent tuberculosis infection were found. TB infection in the household may predict of TST conversion of his/her partner later in life.