Table 2 Potential pitfalls in research on rates of evidence-based practice

The interventions themselves do not carry a grade, it is their application in the appropriate clinical circumstances that earns them the relevant evidence grade. For example, a hysterectomy for menorrhagia may be appropriately graded A only when less invasive options have been exhausted. This problem may not be dealt with by pairing up interventions with diagnoses without regard for previous history of the problem.

Selection of main diagnosis-intervention set

By narrowing down to one main set other aspects of care that might be important might be excluded. An alternate approach would be to develop care-pathways based on evidence and study compliance with pathway as a measure of evidence-based practice.

Multi-faceted interventions

Some interventions are a composite of several aspects of care, e.g. management of labour consists of amniotomy, augmentation, support, etc. Each aspect of care may be evidence based but it may be difficult to provide a single grade to the composite intervention.

Coding of diagnosis-intervention sets

Coding using the International Statistical Classification of Diseases and Related Health Problems (ICD-10) (WHO, 1992) can produce confusing sets, e.g. vertex presentation and normal delivery. Here the delivery is an outcome not an intervention. The intervention is care according to labour ward guideline. Sometimes such sets could be so confusing that they cannot qualify for an evidence search.

Unit of analysis

If admission is used as the unit of analysis instead of patient this might bias the analysis. It is possible that the same patient may be counted more than once if they are admitted on several occasions over the study period. Using short sampling periods may avoid this problem.

Self evident interventions

These are interventions where there are no controlled trials in support of the treatment modality but there is convincing biological or basic research evidence such that a trial would be unnecessary or unethical, e.g. caesarean section for placenta praevia. These should not be graded as Grade C.

Cost-effectiveness of care

Cost-effectiveness rather than effectiveness alone may determine provision of care. Some cases may be graded lower on the grounds that the marginal benefit of an intervention graded higher is not considered worthy of the additional expense involved.