Methods and recommendations for evaluating and reporting a new diagnostic test.

No standardized guidelines exist for the biostatistical methods appropriate for studies evaluating diagnostic tests. Publication recommendations such as the STARD statement provide guidance for the analysis of data, but biostatistical advice is minimal and application is inconsistent. This article aims to provide a self-contained, accessible resource on the biostatistical aspects of study design and reporting for investigators. For all dichotomous diagnostic tests, estimates of sensitivity and specificity should be reported with confidence intervals. Power calculations are strongly recommended to ensure that investigators achieve desired levels of precision. In the absence of a gold standard reference test, the composite reference standard method is recommended for improving estimates of the sensitivity and specificity of the test under evaluation.

The Maryland aggregate pathology index: a deceased donor kidney biopsy scoring system for predicting graft failure.

Despite the common use of diagnostic pretransplant deceased donor kidney biopsy, there is no consensus on the prognostic significance of the pathologic findings. In order to assist clinicians with interpretation we analyzed 371 pretransplant biopsies and correlated the findings with graft failure. Glomerular pathology was assessed with percent glomerulosclerosis (GS), glomerular size and periglomerular fibrosis (PGF); vascular pathology with arterial wall-to-lumen ratio (WLR) and arteriolar hyalinosis and interstitial pathology with measurement of cumulative fibrosis and presence of scar. Using two-thirds of the study population as a model-development cohort, we found that biopsy features independently associated with an increased risk of graft failure were GS > or =15%, interlobular arterial WLR > or =0.5 and the presence of PGF, arteriolar hyalinosis or scar. The Maryland Aggregate Pathology Index (MAPI), was developed from these parameters and validated on the remaining one-third of the population. Five-year actuarial graft survival was 90% for kidneys with MAPI scores between 0 and 7, 63% for scores from 8 to 11 and 53% for scores from 12 to 15 (p < 0.001). We conclude MAPI may help transplant physicians estimate graft survival from the preimplantation biopsy findings, in clinical situations similar to this study population (cold ischemia over 24 h, GS < 25%).