Pilot study of ultrasound parotid imaging reporting and data system (PIRADS): Inter-observer agreement

• Parotid focal lesions classified into nine patterns and then categorized into five groups: PIRADS 1, definitively benign; PIRADS 2, probably benign; PIRADS 3, indeterminate; PIRADS 4, probably malignant; and PIRADS 5, highly suggestive malignancy.
• There was excellent interobserver agreement of both readers for patterns and PIRADS (K = 0.84, P = 0.001) with 92% percent agreement.
• The proposed PIRADS has a role in categorizing parotid lesions and prediction of malignancy.

AimTo establish proposal ultrasound parotid imaging reporting and data system (PIRADS) for classification and prediction of malignancy of parotid lesions and to assess the inter-observer agreement of this system.Subjects and methodsRetrospective analysis of ultrasound and power Duplex images of 142 patients with parotid lesions by two reviewers. Parotid focal lesions were classified into nine patterns and then categorized into five groups: PIRADS 1, definitively benign; PIRADS 2, probably benign; PIRADS 3, indeterminate; PIRADS 4, probably malignant; and PIRADS 5, highly suggestive malignant.The resultsThere was excellent interobserver agreement of both reviewers for patterns and PIRADS (K = 0.84, P = 0.001) with 92% percent agreement. There was excellent agreement of PIRADS 1 (K = 1.00, P = 0.001), PIRADS 2 (K = 0.97, P = 0.001), PIRADS 3 (K = 0.86, P = 0.001) and PIRADS 5 (K = 0.88, P = 0.001) and good agreement of PIRADS 4 (K = 0.67, P = 0.001). The Odds ratio of PIRADS 3, 4 and 5 were 1.36 (95% CI = 0.39–4.55), 7.11 (95% CI = 3.02–11.15) and 8.27 (95% CI = 3.49–10.27) respectively. The accuracy was 92% and 90%, sensitivity was 79% and 65%, specificity was 94% and 96% of PIRADS of both reviewers respectively.ConclusionThe proposed PIRADS is a reliable non-invasive imaging modality that can be used for categorizing parotid lesions and prediction of malignancy.

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