Inter-and intra-reader reliability of 99mTc- DMSA planar vs. SPECT/CT scintigraphy in the detection of renal cortical defects

Aim: The aim of this study was to detect inter- and intra-reader reliability of 99mTc-DMSA planar vs. SPECT/CT scintigraphy in patients with suspected renal cortical scarring.
Patients and methods: Patients with clinically suspected renal scarring were prospectively included. The 99mTc-DMSA planar scintigraphy was obtained 2-4 hours after I.V injection of 185 MBq of the tracer. The SPECT/CT images were obtained immediately after the planar one. The images were independently and blindly interpreted by two experienced nuclear medicine physicians (R1; first reader and R2; second reader). Both planar and SPECT/CT images were scored as 0; normal, 1; equivocal, and 2; positive defects. The readings of both readers were compared.
Results: A total of 186 kidneys were eligible for analysis. In planar imaging, R1 identified 113 normal kidneys, 27 equivocal lesions, and 46 positive defects, while R2 identified 92 normal kidneys, 13 equivocal lesions, and 81 positive defects. The two readers agreed on the readings of 133 kidneys and disagreed on the readings of 53 lesions, with a Kappa value of 0.510.
The second planar reading for R1 detected 117 normal, 27 equivocal lesions, and 42 positive defects. The first and second planar readings for R1 agreed on the readings of 168 kidneys and disagreed on the readings of 18 lesions, with a Kappa value of 0.831.
SPECT/CT readings of R1 identified 126 normal kidneys and 60 positive defects, while R2 identified 101 normal kidneys and 85 positive defects. The two readers agreed on the readings of 149 kidneys and disagreed on the readings of 37 lesions, with a Kappa value of 0.590. The second SPECT/CT reading for R1 detected 129 normal and 57 positive defects. The first and second SPECT/CT readings for R1 agreed on the readings of 173 kidneys and disagreed on the readings of 13 others, with a Kappa value of 0.840.
Conclusion: 99mTc-DMSA SPECT/CT scanning had superior inter-reader yet similar intra-reader reliability to traditional planar imaging for detecting renal cortical scarring.