Assessment of FUS-200 Performance: Comparison with Quantitative Urine Culture Shows that Identifying the Right Cutoff for Optimizing Analyzer Performance Is Challenging

Abstract

Abstract Background Urine sediment analysis is a frequently ordered test, since it permits screening for many clinical conditions. Here, the technical and bacteriuria diagnostic performance of FUS-200, a new sediment analyzer, was assessed. Methods Carry-over, imprecision, and linearity were measured according to CLSI protocols. FUS-200 was compared to sediMAX™, our current laboratory analyzer, in terms of particle recognition/counting in 382 fresh urine samples, and bacteriuria diagnosis was based on white blood cell (WBC) and bacteria counts in a subgroup of the same samples. In the diagnostic study, quantitative bacterial cultures served to classify the samples as bacteria-positive or bacteria-negative. Results FUS-200 did not show carryover for the particles tested. Total imprecision for red blood cells (RBCs) and WBCs in positive controls was 3.6%–10.5% and complied with European guidelines. RBC and WBC recovery was linear. When FUS-200 particle counts were edited by a reviewer, concordance with sediMAX improved for epithelial cells, yeast, and crystals, and recognition of casts and crystals improved. FUS-200 concordance with sediMAX varied between 97% for yeast and 58% for bacteria and was satisfactory. FUS-200 detected bacteriuria better than sediMAX (P = 0.004). FUS-200 WBC and bacteria cutoff values based on the Youden index detected bacteriuria better than manufacturer cutoffs. The best sensitivity with which FUS-200 detected bacteriuria was 79%. Conclusions Although casts and crystal recognition should be improved, the overall technical performance of FUS-200 was acceptable to good. FUS-200 exhibited good screening accuracy for bacteria and WBC. Editing only mildly influenced FUS-200 outcomes.