Smoked drug use in patients with TB is associated with higher bacterial burden

BACKGROUND: Smoking of illicit drugs may lead to more rapid TB disease progression or late treatment presentation, yet research on this topic is scant. We examined the association between smoked drug use and bacterial burden among patients newly initiated on drug-susceptible TB (DS-TB) therapy.METHODS: Data from 303 participants initiating DS-TB treatment in the Western Cape Province, South Africa, were analyzed. Smoked drug use was defined as self-reported or biologically verified methamphetamine, methaqualone and/or cannabis use. Proportional hazard and logistic regression models (adjusted for age, sex, HIV status and tobacco use) examined associations between smoked drug use and mycobacterial time to culture positivity (TTP), acid-fast bacilli sputum smear positivity and lung cavitation.RESULTS: People who smoked drugs (PWSD) comprised 54.8% (n = 166) of the cohort. TTP was faster for PWSD (hazard ratio 1.48, 95% CI 1.10-1.97; P = 0.008). Smear positivity was higher among PWSD (OR 2.28, 95% CI 1.22-4.34; P = 0.011). Smoked drug use (OR 1.08, 95% CI 0.62-1.87; P = 0.799) was not associated with increased cavitation.CONCLUSIONS: PWSD had a higher bacterial burden at diagnosis than those who do not smoke drugs. Screening for TB among PWSD in the community may facilitate earlier linkage to TB treatment and reduce community transmission.

Methods for handling missing data in serially sampled sputum specimens for mycobacterial culture conversion calculation

BACKGROUND

The occurrence and timing of mycobacterial culture conversion is used as a proxy for tuberculosis treatment response. When researchers serially sample sputum during tuberculosis studies, contamination or missed visits leads to missing data points. Traditionally, this is managed by ignoring missing data or simple carry-forward techniques. Statistically advanced multiple imputation methods potentially decrease bias and retain sample size and statistical power.

METHODS

We analyzed data from 261 participants who provided weekly sputa for the first 12 weeks of tuberculosis treatment. We compared methods for handling missing data points in a longitudinal study with a time-to-event outcome. Our primary outcome was time to culture conversion, defined as two consecutive weeks with no Mycobacterium tuberculosis growth. Methods used to address missing data included: 1) available case analysis, 2) last observation carried forward, and 3) multiple imputation by fully conditional specification. For each method, we calculated the proportion culture converted and used survival analysis to estimate Kaplan-Meier curves, hazard ratios, and restricted mean survival times. We compared methods based on point estimates, confidence intervals, and conclusions to specific research questions.

RESULTS

The three missing data methods lead to differences in the number of participants achieving conversion; 78 (32.8%) participants converted with available case analysis, 154 (64.7%) converted with last observation carried forward, and 184 (77.1%) converted with multiple imputation. Multiple imputation resulted in smaller point estimates than simple approaches with narrower confidence intervals. The adjusted hazard ratio for smear negative participants was 3.4 (95% CI 2.3, 5.1) using multiple imputation compared to 5.2 (95% CI 3.1, 8.7) using last observation carried forward and 5.0 (95% CI 2.4, 10.6) using available case analysis.

CONCLUSION

We showed that accounting for missing sputum data through multiple imputation, a statistically valid approach under certain conditions, can lead to different conclusions than naïve methods. Careful consideration for how to handle missing data must be taken and be pre-specified prior to analysis. We used data from a TB study to demonstrate these concepts, however, the methods we described are broadly applicable to longitudinal missing data. We provide valuable statistical guidance and code for researchers to appropriately handle missing data in longitudinal studies.

Alcohol and Tobacco Use in a Tuberculosis Treatment Cohort during South Africa's COVID-19 Sales Bans: A Case Series

BACKGROUND

South Africa temporarily banned alcohol and tobacco sales for about 20 weeks during the COVID-19 lockdown. We described changes in alcohol and tobacco consumption after implementation of these restrictions among a small number of participants in a tuberculosis treatment cohort.

METHOD

The timeline follow-back procedure and Fägerstrom test for nicotine dependence was used to collect monthly alcohol and tobacco use information. We report changes in heavy drinking days (HDD), average amount of absolute alcohol (AA) consumed per drinking day, and cigarettes smoked daily during the alcohol and tobacco ban compared to use prior to the ban.

RESULTS

Of the 61 participants for whom we have pre-ban and within-ban alcohol use information, 17 (27.9%) reported within-ban alcohol use. On average, participants reported one less HDD per fortnight (interquartile range (IQR): -4, 1), but their amount of AA consumed increased by 37.4 g per drinking occasion (IQR: -65.9 g, 71.0 g). Of 53 participants who reported pre-ban tobacco use, 17 (32.1%) stopped smoking during the ban. The number of participants smoking >10 cigarettes per day decreased from 8 to 1.

CONCLUSIONS

From these observations, we hypothesize that policies restricting alcohol and tobacco availability seem to enable some individuals to reduce their consumption. However, these appear to have little effect on the volume of AA consumed among individuals with more harmful patterns of drinking in the absence of additional behavior change interventions.