Abstract

Background: A false-positive screening result is associated with harmful treatment or follow-up costs. This study aimed to estimate the rate of false positive proteinuria with the dipstick in patients with systemic lupus erythematosus (SLE) taking hydroxychloroquine.
Methods: A total of 334 patients with a positive dipstick and confirmed by total urine protein with quantification assay were enrolled. The experimental group included those with SLE taking hydroxychloroquine, and the rest was the control group. The difference of the rate of false positive in the dipstick was analyzed using the chi-square test and odds ratio (OR) between groups. Qualitative tracking of potential interference in the dipstick was performed.
Results: The results revealed that the rate of false positive with a dipstick for the experimental and control groups were 29.5% and 5.0% (p = 0.000), respectively. The OR with 95% confidence interval (CI) of the rate of false positive for the experimental group with respect to the control group was 5.95 (95% CI: 2.80 - 12.65). Qualitative tracking showed that the dipstick was influenced to become false-positive when hydroxychloroquine concentration was ≥ 30 mg/dL.
Conclusions: Hydroxychloroquines like plaquenil or geniquin may lead to a high rate of false positive with the dipstick method. A quantification assay is recommended for proteinuria measurement in patients with SLE taking hydroxychloroquines.

DOI: 10.7754/Clin.Lab.2014.140706