Women with an abnormal Pap smear are often referred to colposcopy, a procedure during which endocervical curettage (ECC) may be performed. ECC is a scraping of the endocervical canal lining. Our goal was to compare the performance of a naïve Poisson (NP) regression model with that of a zero-inflated Poisson (ZIP) model when identifying predictors of the number of distress/pain vocalizations made by women undergoing ECC. Data on women seen in the colposcopy clinic at a medical school in El Paso, Texas, were analyzed. The outcome was the number of pain vocalizations made by the patient during ECC. Six dichotomous predictors were evaluated. Initially, NP regression was used to model the data. A high proportion of patients did not make any vocalizations, and hence a ZIP model was also fit and relative rates (RRs) and 95% CIs were calculated. AIC was used to identify the best model (NP or ZIP). Of the 210 women, 154 (73.3%) had a value of 0 for the number of ECC vocalizations. NP identified three statistically significant predictors (language preference of the subject, sexual abuse history and length of the colposcopy), while ZIP identified one: history of sexual abuse (yes vs no; adjusted RR=2.70, 95% CI 1.47 to 4.97). ZIP was preferred over NP. ZIP performed better than NP regression. Clinicians and epidemiologists should consider using the ZIP model (or the zero-inflated negative binomial model) for zero-inflated count data.
- genital diseases, female
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Presented at The abstract was presented as a poster (number LB05) at the Annual Meeting of the American College of Epidemiology, in Decatur, Georgia, on September 28, 2015.
Contributors MF offered overall project leadership. CGB, TC, LF, and MF collected the data. TC and CGB managed the data. ZDM analyzed the data. ZDM drafted the initial manuscript. All authors offered input on the study results and offered critical input and review, which led to the creation of the final version of the manuscript.
Funding This study was supported in part by the National Institutes of Health award P01 CA082710-13 (Optical Technologies and Molecular Imaging for Cervical Neoplasia) and the Department of Obstetrics and Gynecology, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center El Paso, El Paso, Texas.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Our study was approved by the Institutional Review Board for the Protection of Human Subjects, Texas Tech University Health Sciences Center at El Paso (approval number E12117).
Provenance and peer review Not commissioned; externally peer reviewed.
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