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  • Author or Editor: Gabriele Rossi x
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Abstract

OBJECTIVE To assess sensitivity and specificity of manual and automated measurements of reticulocyte percentage, number, and production index for classification of anemia in dogs.

DESIGN Retrospective case series

SAMPLE 174 blood smears from client-owned dogs with anemia collected between 1993 and 2013 for which reticulocyte parameters were determined manually (nonregenerative anemia, 22; preregenerative anemia, 23; regenerative anemia, 28) or with an automated laser-based counter (nonregenerative anemia, 66; preregenerative anemia, 17; regenerative anemia, 18).

PROCEDURES Diagnostic performance was evaluated with receiver operating characteristic (ROC) curves by considering preregenerative anemia as nonregenerative or regenerative. Sensitivity, specificity, and positive likelihood ratio were calculated by use of cutoffs determined from ROC curves or published reference limits.

RESULTS Considering preregenerative anemia as non regenerative, areas under the curve (AUCs) for reticulocyte percentage, number, and production index were 97%, 93%, and 91% for manual counting and 93%, 90%, and 93% for automated counting. Sensitivity, specificity, and positive likelihood ratio were 82% to 86%, 82% to 87%, and 4.6 to 6.4, respectively. Considering preregenerative anemia as regenerative, AUCs were 77%, 82%, and 80% for manual counting and 81%, 82%, and 92% for automated counting. Sensitivity, specificity, and positive likelihood ratio were 72% to 74%, 76 to 87%, and 2.7 to 6.2, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE Whereas all reticulocyte parameters identified regeneration in anemic dogs, the performance of specific parameters was dependent on the method used. Findings suggested that lower cutoffs than published reference limits are preferred for reticulocyte number and production index and higher cutoffs are preferred for reticulocyte percentage. Reticulocyte production index may be useful when the pretest probability of regeneration is moderate.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether preanalytic and analytic factors affect evaluation of the urinary protein-to-creatinine (UPC) ratio in dogs.

Sample—50 canine urine samples.

Procedures—The UPC ratio was measured to assess the intra-assay imprecision (20 measurements within a single session), the influence of predilution (1:10, 1:20, and 1:100) for urine creatinine concentration measurement, and the effect of storage at room temperature (approx 20°C), 4°C, and −20°C.

Results—The coefficient of variation at room temperature determined with the 1:20 predilution was < 10.0%, with the highest coefficients of variation found in samples with a low protein concentration or low urine specific gravity. This variability could result in misclassification of samples with UPC ratios close to the thresholds defined by the International Renal Interest Society to classify dogs as nonproteinuric (0.2), borderline proteinuric (0.21 to 0.50), or proteinuric (> 0.51). A proportional bias was found in samples prediluted 1:10, compared with samples prediluted 1:20 or 1:100. At room temperature, the UPC ratio did not significantly increase after 2 and 4 hours. After 12 hours at room temperature and at 4°C, the UPC ratio significantly increased. The UPC ratio did not significantly change during 3 months of storage at −20°C.

Conclusions and Clinical Relevance—The intra-assay precision of the UPC ratio was sufficiently low to avoid misclassification of samples, except for values close to 0.2 or 0.5. The optimal predilution ratio for urine creatinine concentration measurement was 1:20. A 1:100 predilution is recommended in samples with a urine specific gravity > 1.030. The UPC ratio must be measured as soon as samples are collected. Alternatively, samples should be immediately frozen to increase their stability and minimize the risk of misclassification of proteinuria.

Full access
in American Journal of Veterinary Research