Household ventilation and tuberculosis transmission in Kampala, Uganda

OBJECTIVE

To test the feasibility of measuring household ventilation and evaluate whether ventilation is associated with tuberculosis (TB) in household contacts in Kampala, Uganda.

DESIGN

Adults with pulmonary TB and their household contacts received home visits to ascertain social and structural household characteristics. Ventilation was measured in air changes per hour (ACH) in each room by raising carbon dioxide (CO₂) levels using dry ice, removing the dry ice, and measuring changes in the natural log of CO₂ (lnCO2) over time. Ventilation was compared in homes with and without co-prevalent TB.

RESULTS

Members of 61 of 66 (92%) households approached were enrolled. Households averaged 5.4 residents/home, with a median of one room/home. Twelve homes (20%) reported co-prevalent TB in household contacts. Median ventilation for all rooms was 14 ACH (interquartile range [IQR] 10-18). Median ventilation was 12 vs. 15 ACH in index cases' sleeping rooms in households with vs. those without co-prevalent TB (P = 0.12). Among smear-positive indexes not infected by the human immunodeficiency virus (HIV), median ventilation was 11 vs. 17 ACH in index cases' sleeping rooms in homes with vs. those without co-prevalent TB (P = 0.1).

CONCLUSION

Our findings provide evidence that a simple CO₂ decay method used to measure ventilation in clinical settings can be adapted to homes, adding a novel tool and a neglected variable, ventilation, to the study of household TB transmission.

Significant variation in presentation of pulmonary tuberculosis across a high resolution of CD4 strata

BACKGROUND

The human immunodeficiency virus (HIV) alters the presentation of pulmonary tuberculosis (PTB), but it remains unclear whether alterations occur at a CD4 cell threshold or throughout HIV infection.

OBJECTIVE

To better understand the relationship between CD4 count and clinical and radiographic presentation of PTB.

SETTING AND DESIGN

Initial presentations of culture-confirmed PTB patients evaluated at a Ugandan national TB referral center and an affiliated research unit were compared by HIV status and across 11 CD4 cell count strata: 0-50 to >500 cells/μl.

RESULTS

A total of 873 HIV-infected PTB cases were identified. Among HIV-infected PTB cases with CD4 < 50, 21% had a normal chest X-ray (CXR) vs. 2% with CD4 > 500, with a continuous trend across CD4 strata (test for trend, P < 0.001). All radiographic manifestations of PTB displayed significant trends across CD4 strata. HIV-infected vs. non-HIV-infected patients had no significant difference in CXR findings of miliary patterns or pleural effusion at CD4 > 100, normal CXR or fibrosis at CD4 > 150, adenopathy at CD4 > 250, and cavitation or upper lung disease at CD4 > 300. Twenty-three per cent of co-infected cases with CD4 < 50 and 1% with CD4 > 500 had negative acid-fast bacilli (AFB) smears, with a significant trend between (P < 0.001).

CONCLUSION

Variations in CXR appearance and AFB smear correlate with CD4 decline in significant, continuous trends.