E. Girardi et al., ASSOCIATION OF TUBERCULOSIS RISK WITH THE DEGREE OF TUBERCULIN REACTION IN HIV-INFECTED PATIENTS, Archives of internal medicine, 157(7), 1997, pp. 797-800
Background: The risk of developing active tuberculosis associated with
a different size of induration to purified protein derivative (PPD) h
as not been prospectively assessed among individuals infected with hum
an immunodeficiency virus (HIV). The quantification of this risk is im
portant to more appropriately identify candidates for preventive thera
py for tuberculosis. Methods: A prospective, multicenter, cohort study
on tuberculosis in HIV-infected patients was conducted in 23 infectio
us disease units in public hospitals in Italy. Two thousand six hundre
d ninety-five HIV-infected patients were enrolled in the study. Of the
se, 1054 patients who were nonanergic at the time of entry were includ
ed in the present analysis. The median duration of follow-up was 102 w
eeks. The main outcome measure was a diagnosis of active tuberculosis
confirmed by the isolation of Mycobacterium tuberculosis in culture. R
esults: Among the 252 patients with PPD reactivity, patients with an i
nduration to PPD of 2 to 4 mm had a median CD4(+) lymphocyte count of
0.34x10(9)/L (interquartile [IQ] range, 0.14x10(9)-0.56x10(9)), those
with a response of 5 to 9 mm had a median count of 0.38x10(9)/L (IQ ra
nge, 0.24x10(9)-0.56x10(9)), and those with a response of 10 mm or hig
her had a median count of 0.37x10(9)/L (IQ range, 0.23x10(9)-0.52x10(9
)) (P=.38). Compared with the 802 nonanergic PPD-negative patients, ha
zard ratios of tuberculosis were 2.1 (95% confidence interval [CI], 0.
2-18.3) among the 55 patients with a response to PPD of 2 to 4 mm, 5.7
(95% CI, 1.6-19.8) among the 128 patients with a response to PPD of 5
to 9 mm, and 23.1 (95% CI, 7.8-68.6) among the 69 patients with a res
ponse to PPD of 10 mm or higher. Conclusions: Among nonanergic HIV-inf
ected patients, the degree of response to tuberculin does not appear t
o reflect the degree of immunosuppression and is strongly correlated w
ith the subsequent incidence of tuberculosis. To identify HIV-infected
patients who are at an increased risk of tuberculosis and may benefit
from preventive therapy, a response to PPD of 5 mm appears to be an a
ppropriate cutoff point.