Evaluation of Heller's reaction and the urine dipstick method alone or in combination to detect proteinuria in sheep

Abstract

Urine dipstick and Heller's reaction are easy first-line screening tests for the detection of proteinuria; however, the performance of these methods in alkaline ovine urine is largely unknown. The aim of this study was to evaluate the diagnostic performance of Heller's reaction alone or in combination with dipstick for the detection of proteinuria in sheep, using the urine protein to creatinine ratio (UP/C) with two cut-off values as the reference method. Ninety-eight urine samples were collected from sheep using the transient apnea method. Heller's reaction, the dipstick method, and the UP/C ratio were used to assess proteinuria. The results were statistically analyzed twice, based on two different UP/C cut-off values of 0.2 and 0.5. Cohen's kappa value was used to determine the agreement between the UP/C ratios and Heller's reaction, the dipstick method, or the combination of methods. Sensitivity, specificity, and positive and negative likelihood ratios were calculated. ROC curves were also generated, and the areas under the curve (AUC) were evaluated to determine the optimal threshold for the numerical values of the two methods. Heller's reaction is more specific (96.67% and 96.00% when the cut-off value is 0.2 and 0.5, respectively) than the dipstick method, while the dipstick method was more sensitive (91.18% and 91.30%, when the cut-off value was 0.2 and 0.5, respectively) than Heller's reaction for the detection of proteinuria. Both tests were accurate when any grade >0 was considered positive. Proteinuria can almost be excluded in ovine urine samples with negative Heller's reaction and dipstick test.