Culture-negative TB: Clinical Characteristics, Risk Factors and Treatment Outcomes

Background: Although culture remains the standard for TB diagnosis, 15–20% of patients diagnosed and treated for TB are culture-negative. We explored clinical characteristics, risk factors and treatment outcomes for culture-negative TB in a Peruvian cohort.

Methods: We recruited 4,500 index TB patients and 10,160 household contacts in Lima, Peru, and enrolled 692 secondary patients diagnosed with TB during follow-up of household contacts. We analyzed smear and culture status, sociodemographic factors, clinical characteristics and TB treatment outcomes to compare culture-negative and positive patients.

Results: Of the 4,880 adult patients, 915 (18.8%) were culture-negative. Culture-negative patients were less likely to report symptoms of TB disease and disease of longer duration. A multivariate analysis showed no statistically significant difference in loss to follow-up, treatment failure or recurrence between the culture-negative and -positive groups but a higher rate of death among culture-negative patients with an adjusted OR of 1.65 (95% CI 1.05–2.60). In a multivariate analysis of determinants of culture negativity, older age, substance use and being a secondary case were associated with culture status.

Conslusion: More recognition and awareness of culture-negative TB is key for early and correct diagnosis to reduce transmission and improve treatment outcomes.