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Table 1 Classification of evidence.

From: A Dutch guideline for the treatment of scoliosis in neuromuscular disorders

Papers concerning interventions (prevention or therapy)

A1

Systematic reviews discussing at least a few studies of A2-level, and in which the results of the distinctive studies discussed are consistent;

A2

Randomized controlled trials (RCTs) of good quality (randomized double blind controlled trials) involving a sufficient number of subjects, and employing suitable research methods;

B

Generally consistent findings of weaker scientific studies (not randomized, comparative cohort studies, patient -control studies);

C

non-comparative studies;

D

expert opinions.

Papers concerning diagnosis

A1

Prospective studies of the effects of diagnostics on clinical outcome in a well defined patient group. The outcome parameters are well defined in advance.

 

Good quality studies of decision-making with respect to diagnostics and clinical outcomes;

A2

Studies of diagnostic tests compared to a reference test. Criteria and outcomes are well-defined in advance, and the test and the study population are adequately described. The study population must be sufficiently large. Independent observers have assessed the test results. The experimental and reference tests are evaluated independently. In cases where multiple diagnostic tests are used, the analysis should be adapted for interdependency of the results (e.g. by using logistic regression);

B

Studies of diagnostic tests compared to a reference test. The test and population are described but the study is of less quality than described in level A;

C

non-comparative studies;

D

expert opinions.