TREATMENT OF CONTINUOUS DATA AS CATEGORIC VARIABLES IN OBSTETRICS ANDGYNECOLOGY

Objective: To assess the treatment of continuous data in a sample of o bstetric and gynecologic literature. Methods: We reviewed articles in Obstetrics and Gynecology published in the first 4 months of 1985 and 1995. Data were tabulated on a data form created specifically for this purpose and reviewed for accuracy. Results: The sample set included 1 70 variables in 102 original articles from Obstetrics and Gynecology p ublished from January to April 1995, inclusive (group A, contemporary articles), and 117 variables in 89 articles published between January and April 1985, inclusive (group B, historic articles). Fifty-three va riables (31% of total variables) in group A and 27 variables (23% of t otal variables) in group B (chi(2) P = .05) were continuous predictor variables. The historic-period articles (63%) were significantly more likely to represent continuous data only as categoric variables than w ere articles in the contemporary period (38%) (Fisher exact test, P = .037). Correlation coefficients, r values, were provided where possibl e in ten articles in the contemporary period (83%) and four articles i n the historic period (31%) (Fisher exact test, P = .008). In articles in which continuous predictors were treated only as categoric variabl es, an emphasis was placed on the findings based only on categories in four of 12 (33%) of these articles in 1995 and nine of 13 (69%) in 19 85 (Fisher exact test, P = .05). Conclusions: The treatment of continu ous data has improved over the time period reviewed. However, clinicia ns should be aware that continuous data may be mischaracterized as cat egoric variables in some journal articles. We hope that in the future, editors will consider requesting r values for all continuous data rel ations. The quality-of-care implications of using discrete cutoffs of continuous data for patient care should be investigated. Copyright (C) 1997 by The American College of Obstetricians and Gynecologists.