Reliability of DMSA for the diagnosis of kidney damage in children

JC Craig, L Irwig, M Ford, N Willis, RB Howman-Giles, RF Uren, MA Rossleigh, S Grunewald

Centre for Kidney Research, Royal Alexandra Hospital for Children, Westmead NSW, Australia

The objective of this study was to evaluate the variability of DMSA scintigraphy interpretation by four nuclear medicine physicians for the diagnosis of renal parenchymal abnormality in children and to compare variability among three different DMSA methods in clinical use; planar alone, single photon emission computerized tomography (SPECT) alone, and planar with SPECT. One-hundred consecutive DMSA scintiscans were independently interpreted three times by four participating nuclear medicine specialists from different departments and in random order. All scans were classified by whether renal parenchymal abnormality was present or absent and using a modified four level grading system of Goldraich. Indices of agreement were the percentage of agreement and the kappa statistic, which were weighted with integers representing the number of categories from perfect agreement. Disagreement was analysed for children, kidneys and kidney zones (three zones per kidney). For patients as the unit of analysis, agreement for the planar alone and planar with SPECT methods was 86-87% (kappa 74%) for the normal-abnormal scan classification. Agreement for the SPECT alone method was 78% (kappa 57%). The frequency of substantial disagreement (disagreement 2 categories) occurred in 2.5% and 1.3% of comparisons between observers for planar alone and SPECT with planar, but in 5.2% of comparisons for the SPECT alone method ( 2 = 15.4; p < 0.0001). These results did not vary appreciably whether interpretation of patients, kidneys or kidney zones was compared. In conclusion, four experienced nuclear medicine physicians showed excellent agreement in the interpretation of planar alone and planar with SPECT DMSA scintigraphic images. Interpretation of SPECT DMSA images, without planar, was significantly more variable than the two other methods used, so that disagreement occurred in over 20% of comparisons. SPECT DMSA scintigraphy, when used without planar images, does not provide a firm basis for clinical decision making in the care of children who may have renal damage. There is no benefit of reduced variability by the provision of SPECT images to planar scintiscans to nuclear medicine physicians.

Presented at the American Society of Nephrology Philadelphia October 1998

Correspondence
Dr Jonathan Craig
JonC@chw.edu.au