Inter-Rater Reliability of Manual Waist Circumference and Agreement With DXA-Derived Waist in Male Collegiate Rugby Players

Waist circumference (WC) is a low-cost surrogate of central adiposity, but measurement error can limit athlete monitoring. PURPOSE: Evaluate inter-rater reliability of manual WC and agreement with dual-energy X-ray absorptiometry (DXA)-derived WC in male collegiate rugby players. METHODS: Twenty-one male collegiate rugby players completed baseline testing (manual WC and DXA completed same day) following an overnight fast and euhydration. Two trained raters independently measured WC on bare skin at the superior border of the iliac crest (site not pre-marked) using a seca 201 measurement tape, with participants standing feet together and arms relaxed at their sides; the tape was verified horizontal/level around the trunk and measurements were recorded to the nearest 0.1 in following a standardized breathing cue after a normal expiration. Each rater obtained one measurement and was blinded to the other rater's value. Whole-body DXA (Hologic Horizon W; APEX v5.6.1.3 rev 007) generated automated WC and visceral adipose tissue (VAT) estimates. Inter-rater reliability was assessed using ICC (2,1), standard error of measurement (SEM), minimal detectable change (MDC95), paired t-test, and Bland-Altman analysis. Agreement between mean manual WC and DXA WC was evaluated with Pearson correlation and Bland-Altman. RESULTS: Manual WC was 35.5 ± 5.8 in (Rater A) and 35.6 ± 6.0 in (Rater B) with trivial bias (-0.05 ± 0.46 in; p=0.60). Inter-rater reliability was excellent (ICC=0.997; SEM=0.32 in; MDC95=0.88 in) with limits of agreement -0.96 to 0.85 in. DXA WC was 38.4 ± 6.8 in and correlated strongly with manual WC (r=0.969, p CONCLUSION: Manual WC demonstrates near-perfect inter-rater reliability in male collegiate rugby players and is suitable for longitudinal monitoring when standardized. However, DXA- and tape-derived WC are not interchangeable due to systematic bias; consistent methodology is recommended when tracking central adiposity.