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Inter- and Intraobserver Variability of ^99mTc-DMSA Renal Scintigraphy: Impact of Oblique Views

Meltem Caglar¹, Pnar Özgen Kratl¹ and Erdem Karabulut²

¹ Department of Nuclear Medicine, Hacettepe University, Ankara, Turkey; and ² Department of Biostatistics, Hacettepe University, Ankara, Turkey

Correspondence: For correspondence contact: Meltem Caglar, MD, Department of Nuclear Medicine, Hacettepe University, Sihhiye, Ankara, 06100, Turkey. E-mail: mcaglar{at}hacettepe.edu.tr

^99mTc-Dimercaptosuccinic acid (DMSA) scintigraphy is a frequently used diagnostic test to assess the presence and severity of cortical damage. The aim of this study is to investigate the variability in the interpretation of ^99mTc-DMSA scans, evaluate the usefulness of oblique images, and assess their impact on scan interpretation. Methods: Two experienced nuclear medicine physicians independently interpreted 100 ^99mTc-DMSA scans (197 kidneys) 4 times. Interpretation was twice based on posterior projection images and twice based on posterior and posterior oblique projection images. For each kidney, the observers had to choose between the following results: normal, abnormal, and indeterminate. The indices of variability used were the percentage of agreement, -statistic, and marginal homogeneity. Results: Intraobserver and interobserver reproducibility (-values) varied between 0.683 and 0.708 and between 0.609 and 0.671, respectively, for posterior images. Disagreement in ^99mTc-DMSA scan interpretation occurred in 18% of kidneys within observers and in 21% of kidneys between observers when only posterior images were used. Oblique views changed the interpretation in 14% and 11.5% of kidneys for the first and second observers, respectively. The use of oblique views increased the agreement rate within and between observers (-values, 0.725–0.812 and 0.768–0.732, respectively; mean agreement, 86.5 and 87.25, respectively). Conclusion: Oblique views were found useful in approximately 13% of kidneys and affected inter- and intraobserver variability. Our results suggest that oblique views should be used routinely in children with clinically suspected urinary tract infection to reliably interpret images.

Key Words: DMSA; scintigraphy; observer variability