Simplified scoring of the Actionable 8-item screening questionnaire for neurogenic bladder overactivity in multiple sclerosis: a comparative analysis of test performance at different cut-off points

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BACKGROUND: The Actionable questionnaire is an 8-item tool to screen patients with multiple sclerosis (MS) for neurogenic bladder problems, identifying those patients who might benefit from urological referral and bladder-specific treatment. The original scoring yields a total score of 0 to 24 with cut-off point 6. A simplified scoring, yielding a total score of 0 to 8 with cut-off point 3, has been developed in urogynaecological patients, but has not been investigated in MS. METHODS: One-hundred-and-forty-one MS patients completed the Actionable on two occasions. We compared the test performance of the simplified scoring with cut-off point 3 with that of cut-off point 2, using the original scoring with cut-off point 6 as a gold standard. The following measures were calculated: True Positives (TP), True Negatives (TN), False Positives (FP), False Negatives (FN), Sensitivity, Specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPV), and Accuracy. The associations between positive test result and urological treatment, and bladder-specific drug treatment were calculated. RESULTS: For cut-off point 3 the outcomes (Test 1, Test 2) were: TP 43.26 %, 40.88 %; TN 29.79 %, 32.85 %; FP 0.00 %, 0.00 %; FN 26.95 %, 26.28 %; Sensitivity 0.62, 0.61; Specificity 1.00, 1.00; PPV 1.00, 1.00; NPV 0.53, 0.55; Accuracy 0.73, 0.74; and for cut-off point 2: TP 59.57 %, 59.85 %; TN 26.95 %, 31.39 %; FP 2.84 %, 1.46 %; FN 10.63 %, 7.30 %; Sensitivity 0.85, 0.89; Specificity 0.90, 0.96; PPV 0.95, 0.98; NPV 0.72, 0.81; Accuracy 0.87, 0.91. Cut-off 3 completely prevented FP outcomes, but wrongly classified 26 % of the patients as negative (FN). Cut-off 2 reduced the FN to 7-10 %, with low FP values (2.84-1.46 %). With cut-off 2, the percentage of patients screened positive was higher in the Progressive group (75.00 %) than in the Relapsing Remitting group (56.25 %) (P = 0.0331), which was not the case with cut-off 3. Only a positive test according to the original scoring