S. Hunskaar et al., THE JOURNEY OF INCONTINENT WOMEN FROM COMMUNITY TO UNIVERSITY CLINIC - IMPLICATIONS FOR SELECTION BIAS, GATEKEEPER FUNCTION, AND PRIMARY-CARE, Family practice, 13(4), 1996, pp. 363-368
Background. The selection process of patients from community to hospit
als may introduce bias into research and hamper the generalization of
hospital-based research back to general practice. Objective. The objec
tive of this study was to use female urinary incontinence as a model I
n an attempt to provide empirical support fbr selection bias. Method.
The analyses are based on three populations of incontinent women: comm
unity level (epidemiological survey, 535 women), primary care level (g
eneral practice, prospective clinical study, 105 women), and secondary
care level (university hospital, prospective clinical study, 228 wome
n). Results. The general practice patients were older and the hospital
patients younger than those in the community. From community via gene
ral practice to hospital, there was an increase in duration, frequency
of leakage, amount of leakage, severity and perceived impact of incon
tinence. Help-seeking at the primary care level was associated with in
creasing age and severity, and with urge symptoms and substantial impa
ct. Referral from general practice to hospital level was only associat
ed with age and urge symptoms. Conclusion. The study provides empirica
l evidence to support the existence of selection bias. This phenomenon
must not be overlooked when recommendations developed at the consulta
nt level are presented at a level with a significantly different clini
cal picture of a condition.