Impact of hematocrit on point-of-care C-reactive protein-based tuberculosis screening among people living with HIV initiating antiretroviral therapy in Uganda

Abstract

Point-of-care C-reactive protein (POC CRP) testing is a potential tuberculosis (TB) screening tool for people living with HIV (PLHIV). Unlike lab-based assays, POC assays do not routinely adjust CRP levels for hematocrit, potentially resulting in TB screening status misclassification. We compared the diagnostic accuracy of unadjusted and hematocrit-adjusted POC CRP for culture-confirmed TB among PLHIV with CD4 cell-count ≤350 cells/uL initiating antiretroviral therapy (ART) in Uganda. We prospectively enrolled consecutive adults, measured POC CRP (Boditech; normal <8 mg/L), collected two spot sputum specimens for comprehensive TB testing, and extracted pre-ART hematocrit from clinic records. Of the 605 PLHIV included, hematocrit-adjusted POC CRP had similar sensitivity (80% vs 81%, difference +1% [95% CI -3 to +5], P= 0.56) and specificity (71% vs 71%, difference 0% [95% CI -1 to +1], P= 0.56) for culture-confirmed TB, relative to unadjusted POC CRP. When used for TB screening, POC CRP may not require adjustment for hematocrit. However, larger studies may be required if differences close to the clinically meaningful threshold are to be detected.

Keywords: C-reactive protein; Haematocrit; PLHIV; Point of care; Screening; Tuberculosis.