ITEM 4. Describe participant recruitment: Was recruitment based on presenting symptoms, results from previous tests, or the fact that the participants had received the index tests or the reference standard?
An important element of the description is how eligible subjects were identified. Participant recruitment in diagnostic studies can start at different points. Frequently, the study enrolls consecutive patients clinically suspected of the target condition because of presenting symptoms or referral by another health care professional. These patients then undergo the index test(s) as well as the reference standard. Other designs are possible. In some studies, patients are identified after having been subjected to the index test. Other studies start with patients in whom the reference standard established or excluded the presence of the target condition. These patients are then subjected to the index test. Still other studies include both patients already diagnosed with the target condition and participants in whom the condition was excluded. Other studies, often with retrospective data collection, include patients identified by searching hospital records to learn who received the reference standard, or the index test, or both. These alternative study designs are likely to influence the spectrum of disease in included patients, as well as the range and relative frequency of alternative conditions in patients without the target disorder. In the example presented for Item 3, the reasons for attending the family planning clinic were not explicitly stated.
Knottnerus JA, Muris JW. Assessment of the accuracy of diagnostic tests: the cross-sectional study. In: Knottnerus JA, ed. The evidence base of clinical diagnosis. London: BMJ Publishing Group, 2002:39-59.
Sackett DL, Haynes RB. The architecture of diagnostic research. In: Knottnerus JA, ed. The evidence base of clinical diagnosis. London: BMJ Publishing Group, 2002:19-38.
Van der Schouw YT, Van Dijk R, Verbeek AL. Problems in selecting the adequate patient population from existing data files for assessment studies of new diagnostic tests. J Clin Epidemiol 1995;48:417-22.