Journal Home
Search for

Volume 19, Issue 7, Pages 501-503 (July 2009)


View previous. 12 of 17 View next.

Reliability of Retrospectively Assessed Categorical Menstrual Cycle Length Data

Annette M. Bachand, PhDCorresponding Author Informationemail address, Lori A. Cragin, PhD, John S. Reif, MSC, DVM

Received 16 October 2008; accepted 1 March 2009. published online 04 May 2009.

Purpose

Prospective diaries have been shown to be more reliable than retrospective questionnaires for the assessment of menstrual cycle length collected as continuous data. We investigated the reliability of retrospectively collected categorical cycle length data.

Methods

In 2005, 67 women from Illinois and Vermont completed a menstrual diary and retrospective questionnaire. Based on commonly used cutpoints for normal cycle length, we created 2-, 3- and 4-category cycle length variables, calculated percent agreement, Cohen's kappa and prevalence index and investigated factors associated with accurate reporting.

Results

Overall agreement between diary and questionnaire responses was highest for the 2-category cycle length variable, <=35 vs. > 35 days (93%), and the 3-category variable, <25, 25-35 and > 35 days (82%). While Cohen's kappa fell below 0.6, its magnitude was limited by a high prevalence of “normal”" cycle length. Women with regular cycles were slightly more likely to have concordant responses.

Conclusions

In epidemiologic studies where cycle length categories are of interest, the limitations of prospective diaries in terms of cost, compliance, attrition and power must be carefully weighed against the potentially decreased reliability of questionnaire data.

Selected Abbreviations and Acronymsκ, kappa, PI, prevalence index

Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins

Corresponding Author InformationAddress correspondence to: Annette M. Bachand, Colorado State University, Department of Environmental and Radiological Health Sciences, 1681 Campus Delivery, Fort Collins, CO 80523-1681. Tel.: 970-491-3878; fax: 970-491-2940.

PII: S1047-2797(09)00090-8

doi:10.1016/j.annepidem.2009.03.015


View previous. 12 of 17 View next.