Calidad en la etapa preanalítica: evaluación de dos estrategias para verificar la correcta recogida de orina de 24 horas

Introduction

Assessment of the quality of the 24-hour urine sample (urine-24 h) is a challenge in the clinical laboratory. Different strategies based on urinary creatinine excretion have been proposed for the detection of poorly collected samples. The objective of this study was to evaluate the performance of two of these strategies: one based on the reference interval of urinary creatinine excretion (IR-Strategy), and the other one proposed by the Swiss Survey on Salt Group (S-Strategy).

Materials and methods

The study was carried out in the year 2016 with a population from Argentina. A total of 69 adult subjects were included in the study. Complete urine samples (N = 69) and incomplete samples (N = 69) were obtained. These were classified as poor, and well collected, according to the two strategies evaluated. Kappa coefficient, proportion of incorrectly classified samples, and positive and negative likelihood ratios (LR) were calculated. The difference was considered statistically significant for a P < .05. The study was approved by a local Bioethics Committee, and the informed consent was obtained from each participant.

Results

Strategy-IR vs. Strategy-S: Kappa coefficient: 0.26 (95% CI; 0.10-0.42; P = .020) vs. 0.51 (95% CI; 0.37-0.64; P = .000); incorrectly classified samples: 37% vs. 25% (P = .000); positive LR: 1.7 (95% CI; 1.2-2.4) vs. 9.8 (95% CI; 3.7-25.8); negative LR: 0.6 (95% CI; 0.4-0.8) vs. 0.5 (95% CI; 0.4-0.6).

Conclusion

The S-Strategy showed a better performance than the IR-Strategy in the detection of poorly collected urine samples.