The validation of a simple and instrument-free technique to measure the depth of the natal cleft (a cohort study).

Abstract

Pilonidal disease is a benign condition mainly affecting the young population. In recent literature, the depth of the natal cleft is thought to impact postoperative outcomes including wound complications and rate of recurrence. Currently there is no agreed method for measuring the depth of the natal cleft; this study proposes a novel and instrument-free technique that can be used as a research tool to measure the depth. This is a single centre study performed at St Mark's Hospital in London, with 63 participants volunteering to take part. Blinded repeated measurements of the natal cleft were taken by two separate clinicians to assess for inter-observer and intra-observer variation. Agreement was measured and assessed by the Bland-Altman limits of agreement method and intra-class correlation (ICC). The mean difference between repeat measurements for both inter-observer and intra-observer were close to zero (-0.06 and -0.11 respectively). ICC analysis suggested a value of 0.91 for inter-observer agreement, signifying very good agreement between clinicians. Moderate intra-observer agreement was observed, with an ICC value of 0.74. This study offers an alternative simple validated technique to measure the depth of the natal cleft, with good observer agreement. We propose that future studies aiming to analyse the depth of the natal cleft and its relationship with severity and postoperative outcomes use this technique.