Misleading authors' inferences in obstetric diagnostic test literature

OBJECTIVE: Our goal was to determine the validity of authors' inferences ab out the value of the cervicovaginal fetal fibronectin test in the predictio n of preterm birth and the utility of uterine artery Doppler waveform analy sis in the prediction of preeclampsia. STUDY DESIGN: We evaluated all 35 diagnostic test studies (14 on fetal fibr onectin and 21 on uterine artery Doppler) included in 2 meta-analyses. The information on authors' conclusions regarding the value of a positive or ne gative test result was independently abstracted from each article by 2 revi ewers, and it was classified as definitely useful, moderately useful, sligh tly useful, or not at all useful, For the "gold" standard, likelihood ratio s of >10 and <0.1 were regarded as definitely useful, 5 to 10 and 0.1 to 0. 2 were regarded as moderately useful, 2 to 5 and 0.2 to 0.5 were regarded a s slightly useful, and 1 to 2 and 0.5 to 1 were regarded as not at all usef ul. The agreement between the authors and the reference standard was comput ed by simple percentage agreement and weighted kappa statistic. RESULTS: Among articles assessing the diagnostic value of fetal fibronectin the simple agreement between the authors and the "gold" standard was 26% ( 7/26) with a kappa of 0.05 (P = .83), and authors overestimated the value o f the test result in 66% (17/26) of instances. Similarly, among articles as sessing uterine artery Doppler the simple agreement between the authors and the "gold" standard was 31% (13/42) with a ic of 0.28 (P = .31), and autho rs overestimated the value of the test result in 48% (20/42) of instances. CONCLUSION: Authors claimed more positive conclusions than could be support ed by their data. When studies are reported in a misleading manner, the cha nce of misinterpretation on the part of the clinical reader is increased. T he use of explicit criteria that are based on likelihood ratios may reduce the risk of erroneous inferences.