A multicenter trial on interobserver reproducibility in reporting on Tc-99m-DMSA planar scintigraphy: A Belgian survey

Conflicting opinions have been expressed regarding reproducibility in Tc-99 m-dimercaptosuccinic acid (DMSA) planar renal image interpretation. The pur pose of this investigation was to determine the level of interobserver vari ability among a large group of Belgian nuclear medicine physicians who eval uated a randomly selected series of DMSA planar scintigraphic examinations performed on children and adults. Methods: All Belgian nuclear medicine cen ters (n = 82) were invited to participate in a reproducibility study on Tc- 99m-DMSA scintigraphy. Tc-99m-DMSA scans obtained on 10 adults and 40 child ren were randomly selected from the databases of 2 hospitals. Those partici pating in this investigation (65 centers = 79%) received a series of comput er disks containing 50 Tc-99m-DMSA studies. To avoid potential problems rel ated to unfamiliar display, the disks were formatted to be interpretable us ing the participants' own computer systems. Each participant was then free to use his or her usual display (hard copies, contrast enhancement, color s cale, gray scale, and so forth). For each kidney, the observers had to choo se between the following answers: normal, abnormal, equivocal, and lack of quality. Results: Forty-two responses were obtained from a wide variety of institutions and from observers with different levels of experience in inte rpreting Tc-99m-DMSA scintigraphy. Altogether, the following data were obta ined: 60.8% normal, 25.2% abnormal, 7.0% equivocal, and 3.2% lack of qualit y. The median percentage of agreement (overall reproducibility) for the 42 observers was 92%. When the results of all 42 observers were compared, the median agreements on normality and abnormality were 93.5% and 90.5%, respec tively. In a small number (n = 4) of kidneys, reproducibility was poor and ranged from 51% to 70%. Except for 2 outliers, all observers had almost the same level of performance. Conclusion: A large number of Belgian nuclear m edicine physicians participated in evaluating a large randomly selected sam ple of Tc-99m-DMSA studies, and excellent interobserver agreement was found .