Comparison of IDEXX SediVue Dx^® urine sediment analyzer to manual microscopy for detection of casts in canine urine

Background: Detection of urinary casts is difficult due to their intermittent presence and deterioration in urine samples.

Objective: To compare the performance of the IDEXX SediVue Dx^® Urine Sediment Analyzer (SediVue) with manual microscopy for the detection of urinary casts. We hypothesized that the SediVue analyzer would perform similarly to manual microscopy in cast detection.

Animals: Four hundred forty-three samples from 420 dogs from a hospital population.

Methods: This is a prospective, cross-sectional study. For SediVue analysis (software version [SW] 1.0.1.3), uncentrifuged urine was pipetted into a disposable cartridge. Seventy images were captured and processed by an onboard algorithm. For manual microscopy, urine was centrifuged to obtain sediment. Any cast identified by either method was considered a positive result (>0/low-power field [LPF]). SediVue images were evaluated if casts were detected by either methodology. A revised sensitivity and specificity were calculated after image review and when using a threshold of >1 cast/LPF.

Results: The sensitivity of the SediVue analysis for the detection of urinary casts was 53.7% (43.85%-63.35%), and specificity was 86.0% (81.78%-89.51%). After image review, the revised sensitivity/specificity was 52.0% (42.89%-61.02%) and 90.6% (86.81%-93.54%), respectively. When using a more clinically relevant threshold of >1/LPF, the sensitivity was 52.6% (35.82%-69.02%) and specificity was 99.3% (97.85%-99.85%).

Conclusions and clinical importance: The SediVue provides moderate agreement to manual methodology for detection of casts in urine.