Assessment of diastasis recti abdominis: Clinimetric properties of four measuring instruments

Objective: The aim of the study was to determine the intra- and inter-rater reliability of palpation technique, digital calipers, and diastometer, as well as their concurrent validity against ultrasound imaging. Methods: Ninety consenting parous women (20-45 years), recruited from a postnatal clinic in Enugu, Nigeria, participated in this observational study. Two physiotherapists and a sonographer measured their inter rectus distance at the level of the umbilicus, 4.5 cm above and below it, respectively, using each of the four modalities. The intra-rater measurements were taken at a week's interval. Data were analyzed with descriptive and inferential statistics of intraclass correlation coefficient and paired samples T-test, at an alpha level set at P < 0.05. Results: It showed the palpation technique (r = 0.749-0.967 and 0.658-0.917), digital calipers (r=0.750-0.955 and 0.685-0.904), and diastometer (r=0.762-0.958 and 0.471-0.902) demonstrated good inter- and intra-rater reliability. The concurrent validity of the palpation technique, digital calipers, and diastometer against the USI was poor at all three reference points. Conclusion: Palpation technique, digital calipers, and diastometer are reliable tools but not valid substitutes to ultrasound imaging for the clinical measurement of diastasis rectus abdominis.