Survival among patients with HIV infection and smear-negative pulmonary tuberculosis - United States, 1993-2006

Abstract

Background: In patients with HIV and tuberculosis (TB) in resource-constrained settings, smear-negative disease has been associated with higher mortality than smear-positive disease. Higher reported mortality may be due to misdiagnosis, diagnostic delays, or because smear-negative disease indicates more advanced immune suppression.

Methods: We analyzed culture-confirmed, pulmonary TB among patients with TB and HIV in the United States from 1993-2008 to calculate prevalence ratios (PRs) for smear-negative disease by demographic and clinical characteristics. Allowing two years for treatment outcome to be reported, we determined hazard ratios (HRs) for survival by smear status, adjusted for significant covariates on patients before 2006.

Results: Among 16,710 cases with sputum smear results, 6,739 (39%) were sputum smear-negative and 9,971 (58%) were sputum smear-positive. The prevalence of smear-negative disease was lower in male patients (PR: 0.89, 95% confidence interval [CI]: 0.86-0.93) and in those who were homeless (PR: 0.92, CI: 0.87-0.97) or used alcohol excessively (PR: 0.91, CI: 0.87-0.95), and higher in persons diagnosed while incarcerated (PR: 1.20, CI: 1.13-1.27). Patients with smear-negative disease had better survival compared to patients with smear-positive disease, both before (HR: 0.82, CI: 0.75-0.90) and after (HR: 0.81, CI: 0.71-0.92) the introduction of combination anti-retroviral therapy.

Conclusions: In the United States, smear-negative pulmonary TB in patients with HIV was not associated with higher mortality, in contrast to what has been documented in high TB burden settings. Smear-negative TB can be routinely and definitively diagnosed in the United States, whereas high-burden countries often rely solely on AFB-smear microscopy. This difference could contribute to diagnostic and treatment delays in high-burden countries, possibly resulting in higher mortality.

Figure 1. Sputum smear status among patients with HIV and culture-confirmed TB among those with reported sputum smear, United States, 1993–2008.

Black bars indicate the percentage of patients with reported sputum smear result who were smear-positive. Gray bars indicate the percentage of patients with who were smear-negative.

Figure 2. Survival Curves for patients with HIV-infection and culture-confirmed pulmonary TB, by sputum smear result, United States, 1993–2006.

Solid line indicates the Kaplan-Meier survival curve for smear-positive patients. Dotted line indicates the Kaplan-Meier survival curve for smear-negative patients.