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Risk adjustment models for interhospital comparison of CS rates using Robson's ten group classification system and other socio-demographic and clinical variables Full Text
BMC Pregnancy and Childbirth, 07/11/2012
Colais P et al. – The Ten Group Classification System (TGCS) classification is useful for inter–hospital comparison of CS section rates, but residual confounding is present in the TGCS strata.
Methods- The study population includes 64,423 deliveries in Emilia–Romagna between January 1, 2003 and December 31, 2004, classified according to theTGCS.
- Poisson regression was used to estimate crude and adjusted hospital relative risks of CS compared to a reference category.
- Analyses were carried out in the overall population and separately according to the Robson groups (groups I, II, III, IV and V–X combined).
- Adjusted relative risks (RR) of CS were estimated using two risk–adjustment models; the first (M1) including the TGCS group as the only adjustment factor; the second (M2) including in addition demographic and clinical confounders identified using a stepwise selection procedure.
- Percentage variations between crude and adjusted RRs by hospital were calculated to evaluate the confounding effect of covariates.
- The percentage variations from crude to adjusted RR proved to be similar in M1 and M2 model.
- However, stratified analyses by Robson's classification groups showed that residual confounding for clinical and demographic variables was present in groups I (nulliparous, single, cephalic, [greater than or equal to]37 weeks, spontaneous labour) and III (multiparous, excluding previous CS, single, cephalic, [greater than or equal to]37 weeks, spontaneous labour) and IV (multiparous, excluding previous CS, single, cephalic, [greater than or equal to]37 weeks, induced or CS before labour) and to a minor extent in groups II (nulliparous, single, cephalic, [greater than or equal to]37 weeks, induced or CS before labour) and IV (multiparous, excluding previous CS, single, cephalic, [greater than or equal to]37 weeks, induced or CS before labour).
