ABSTRACT
Rationale C-reactive protein (CRP) has demonstrated utility as a point-of-care triage test for tuberculosis (TB) in clinical settings, particularly among people with HIV, but its performance for general-population TB screening is not well characterized. Objective To assess the accuracy of CRP for detecting pulmonary TB disease among individuals undergoing community-based screening or presenting for evaluation of TB symptoms in Kampala, Uganda. Methods We pooled data from two case-control studies conducted between May 2018 and December 2022 among adolescents and adults (>15 years) in Kampala, Uganda. We conducted community-based screening for TB, regardless of symptoms. We enrolled people with Xpert MTB/RIF Ultra-positive (including trace) sputum results and a sample of people with Ultra-negative results. We also enrolled symptomatic patients diagnosed with TB and controls with negative TB evaluations from ambulatory care settings. Participants underwent further evaluation including sputum culture, CRP and HIV testing. We assessed accuracy of CRP alone or with symptom screening, against a bacteriologic reference standard. Our primary analysis evaluated the sensitivity and specificity of CRP at a cutoff of 5 mg/L. Diagnostic performance was summarized by calculating area under the receiver operating curve (AUC). Results In the community setting (N=544), CRP ≥5mg/L had a sensitivity of 55.3% (95% confidence interval: 47.0-63.4) and specificity of 84.7% (79.7-88.8) for confirmed TB; AUC was 0.75 (0.70-0.79). Screening for CRP >5 mg/L or positive symptoms increased sensitivity to 92.0% (86.4-95.8) at the expense of specificity (57.1% [50.8-63.2]). In the ambulatory care setting (N=944), sensitivity of CRP >5 mg/L was 86.7% (81.8-90.7), specificity was 68.6% (64.8-72.2), and AUC (0.84 [0.81-0.87]) did not differ significantly by HIV status. CRP >5 mg/L was >90% sensitive among individuals with a medium or high semiquantitative Xpert result in both settings. Conclusions While CRP did not meet WHO TB screening benchmarks in the community, it demonstrated high specificity, and sensitivity was high among individuals with high sputum bacillary burden who are likely to be most infectious. In ambulatory care, estimated sensitivity and specificity were each within four percentage points of WHO benchmarks with no meaningful difference in performance by HIV status. Primary Source of Funding NIH R01HL138728, R01HL153611.
ABSTRACT
BACKGROUND: Systematic screening is a potential tool for reducing the prevalence of tuberculosis (TB) and counteracting COVID-19-related disruptions in care. Repeated community-wide screening can also measure changes in the prevalence of TB over time. METHODS: We conducted serial, cross-sectional TB case finding campaigns in one community in Kampala, Uganda, in 2019 and 2021. Both campaigns sought sputum for TB testing (Xpert MTB/RIF Ultra) from all adolescents and adults. We estimated the prevalence of TB among screening participants in each campaign and compared characteristics of people with TB across campaigns. We simultaneously enrolled and characterised community residents who were diagnosed with TB through routine care and assessed trends in facility-based diagnosis. RESULTS: We successfully screened 12 033 community residents (35% of the estimated adult/adolescent population) in 2019 and 11 595 (33%) in 2021. In 2019, 0.94% (95% CI: 0.77% to 1.13%) of participants tested Xpert positive (including trace). This proportion fell to 0.52% (95% CI: 0.40% to 0.67%) in 2021; the prevalence ratio was 0.55 (95% CI: 0.40 to 0.75)). There was no change in the age (median 26 vs 26), sex (56% vs 59% female) or prevalence of chronic cough (49% vs 54%) among those testing positive. By contrast, the rate of routine facility-based diagnosis remained steady in the 8 months before each campaign (210 (95% CI: 155 to 279) vs 240 (95% CI: 181 to 312) per 100 000 per year). CONCLUSIONS: Following an intensive initial case finding campaign in an urban Ugandan community in 2019, the burden of prevalent TB as measured by systematic screening had decreased by 45% in 2021, despite the intervening COVID-19 pandemic.
