Variability in the interpretation of dimercaptosuccinic acid scintigraphy after urinary tract infection in children

Abstract

Technetium-99m-dimercaptosuccinic acid (DMSA) scintigraphy is a frequently used diagnostic test in pediatric practice to assess the presence and severity of renal damage. Most commonly it is performed after urinary tract infection. The aim of this study was to investigate the variability in the interpretation of DMSA scans by pediatric nuclear medicine physicians in this clinical setting.

Methods: We selected all 441 scans from children with first-time urinary tract infection who presented between 1993 and 1995 to a pediatric casualty department and who are participants in a prospective cohort study. Two hundred and ninety-four scans were performed at a median time of 7 days after diagnosis, and 147 scans were from children who were free from further infection over a 1-yr follow-up period. Two experienced nuclear medicine physicians independently interpreted the 441 scans according to whether renal damage was present or absent and using the modified 4-level grading system for DMSA abnormality of Goldraich. Apart from being informed that urinary tract infection was the indication for DMSA scintigraphy, no other clinical information was given to the nuclear medicine physicians. The indices of variability used were the percentage of agreement and the kappa statistic. For the grading scale used, both measures were weighted with integers representing the number of categories from perfect agreement. Disagreement was analyzed for children, kidneys and kidney zones.

Results: There was agreement in 86% (kappa = 69%) for the normal-abnormal DMSA scan dichotomy, and the weighted agreement was 94% (weighted kappa = 82%) for the grading of abnormality. Disagreement of DMSA scan interpretation of > or =2 grades was present in three cases (0.7%). The same high level of agreement was present for patient, kidney and kidney zone comparisons. Agreement was not influenced by age or timing of scintigraphy after urinary tract infection.

Conclusion: Two experienced nuclear medicine physicians showed good agreement in the interpretation of DMSA scintigraphy in children after urinary tract infection and using the grading system of Goldraich.