Statistical approaches in the development of clinical practice guidelines from expert panels - The case of laminectomy in sciatica patients

BACKGROUND. Variation in expert opinion and lack of a systematic methodolog y hinder the development of reliable clinical practice guidelines. However standardized protocols have been defined to quantify, combine, and summariz e expert judgments. In addition, statistical methods may help to outline gu idelines based on simplified models of these judgments. METHODS. TO test this hypothesis, stepwise logistic regression (SLR) and cl assification tree pruning (CTP) were used to predict the results of two exp ert panels (USA 1992 and Switzerland 1995) on laminectomy in sciatica condi tions. Both panels, using the RAND-UCLA explicit method, assessed whether t he procedure would be inappropriate or of potential use in 720 case scenari os combining 7 relevant factors. RESULTS. Laminectomy was rated as inappropriate in 60% and 70% of the scena rios by the US and Swiss panels, respectively. Either statistical method, i n both panels, based its simplest model on the same 4 factors, as follows: imaging test results; disability; neurological findings; and conservative t reatment trials (in decreasing order); the influence of 2 other factors, du ration of pain and nerve root irritation, were only marginal. The correct c lassification rates of the models were 89% and 93% for SLR and 93% and 85% for CTP. Adopting the CTP US algorithm as a guideline would lead to conside r performing laminectomy only in patients with imaging evidence of hernia, relatively severe disability, reflex abnormalities, and previous nonsurgica l treatment. Adherence to the corresponding CTP Swiss algorithm would resul t in less restrictive conditions. CONCLUSION. The statistical techniques proved as useful instruments to stru cture and simplify appropriateness criteria developed by expert panels and to outline parsimonious decision models for clinical practice.