Longitudinal reliability of self-reported age at menarche in adolescent girls: variability across time and setting.

Age at menarche is critical in research and clinical settings, yet there is a dearth of studies examining its reliability in adolescents. We examined age at menarche during adolescence, specifically, (a) average method reliability across 3 years, (b) test-retest reliability between time points and methods, (c) intraindividual variability of reports, and (d) whether intraindividual variability differed by setting or individual characteristics. Girls (n = 253) were enrolled in a cross-sequential study in age cohorts (11, 13, 15, and 17 years). Age at menarche was assessed using 3 annual, in-person clinician interviews followed by 9 quarterly phone interviews conducted by research assistants. Reliability of age at menarche across time was moderate and varied by method. In-person interviews showed greater reliability (intraclass correlation coefficient [ICC] = .77) versus phone interviews (ICC = .64). Test-retest reliability in reports did not decrease across time. However, average differences in reported age varied as much as 2.3 years (SD = 2.2 years), with approximately 9% demonstrating differences greater than 4.5 years. Pubertal timing category (i.e., early, late) changed for 22.7% if categorized at the final versus the first report of age at menarche. Reliability was moderate, but average differences in reported age were notable and concerning. Using in-person clinician interviews may enhance reliability. Researchers and clinicians should be cognizant of the implications of using different methods measuring age at menarche when interpreting research findings. PsycINFO Database Record (c) 2013 APA, all rights reserved