General introduction: evaluation of diagnostic procedures

box Whereas the development of diagnostic technologies has greatly accelerated, the methodology of diagnostic research still lags behind that of evaluation of treatment. Diagnostic research appears to be more comprehensive and complex than treatment research as it evaluates the connection between diagnostic and prognostic assessment with choosing optimal interventions. Objectives of diagnostic testing are (1) detecting or excluding disorders, (2) contributing to further diagnostic and therapeutic management, (3) assessing prognosis, (4) monitoring clinical course, and (5) measuring general health or fitness. Methodological challenges include dealing with complex relations, the “gold standard” problem, spectrum and selection bias, “soft” outcome measures, observer variability and bias, optimizing clinical relevance, appropriate sample size, and rapid progress of applicable knowledge over time. Choosing the appropriate study design depends on the research question; the most important designs are the cross-sectional study (to determine the accuracy and added discriminatory value of diagnostic procedures) and the randomized controlled trial (to evaluate the clinical impact of [additional] testing). To synthesize the results of various studies on the same topic, diagnostic systematic reviews and meta-analyses are powerful tools. (continued)