Comparison of IDEXX SediVue Dx(R) 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(R) 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.