The Digital Caliper's Interrater Reliability in Measuring the Interrecti Distance and Its Accuracy in Diagnosing the Diastasis of Rectus Abdominis Muscle in the Third Trimester of Pregnancy.

OBJECTIVE: The purpose of this study was to determine the digital caliper's interrater reliability in measuring the interrecti distance and its accuracy in diagnosing the diastasis of the recti abdomini muscles (DRAM) in the third trimester of pregnancy compared with ultrasound. METHODS: Fifty-four pregnant women were included. Measurements were taken in supine, during trunk flexion and expiration, in the supraumbilical region, in the umbilical scar (US), and in the infraumbilical (IU) region, at first by ultrasonography (USG) and then by the 2 digital caliper's examiners. The 3 evaluators were independent and blind. RESULTS: In the interrecti distance measurement, comparing the 2 calipers' evaluators, the instrument showed an intraclass correlation coefficient (ICC) of 0.86 (95% CI: 0.72-0.92) in the supra-umbilical and ICC of 0.96 (95% CI: 0.92-0.98) in the US. Compared with the USG, the instrument showed the worst interrater reliability in the US (ICC -0.14; 95% CI: -0.39 to 0.13). In diagnosing DRAM, comparing calipers' evaluators, kappa was 0.56 (P < .01) for the IU region and 0.12 (P = .19) for the US region. When compared with the USG, kappa was 0.02 (P = .84) for the IU region and 0.05 (P = .59) for the US. In the US, the caliper presented a positive likelihood ratio of 1.05 (95% CI: 0.86-1.30) and a negative likelihood ratio of 0.63 (95% CI: 0.12-3.43). CONCLUSION: The digital caliper did not present good interrater reliability in measuring or in diagnosing the DRAM during the third trimester of pregnancy compared with ultrasound.