Over Active Bladder Index (OABI): A New Objective Tool Based on Uroflow Parameters for Diagnosis of Overactive Bladder in Children

Abstract

Aims: The aim of this study is to propose an objective uroflow based index for diagnosing over active bladder (OAB).

Materials and methods: Thirty patients with OAB and 30 controls were used in the pilot study. Three uroflow parameters: Uroflow index (UI = Qave/Qmax), voided volume ratio (VVR = voided volume/expected bladder capacity) and time to Q max (TQmax) were studied. Linear regression was performed for the three parameters with controls/OAB patients. Further 28 patients & 32 controls were recruited in a second validation study.

Results: Mean (s.d) UI was 0.7 (0.1) in control while 0.4 (0.1) in OAB (p = 0.001). Mean (s.d) VVR was 0.7 (0.1) in control while 0.5 (0.1) in OAB (p = 0.01). Mean (s.d) TQmax was 5.2 (1.2) in control while 2.1 (1.8) in OAB (p = 0.001). Good correlation was noted with all parameters UI (r = 0.89); VVR (r = 0.87) and TQmax (r = 0.76); when all three were combined as an index the correlation was better (r = 0.95). Based on the beta coefficients an OAB Index [OABI = 8(UI)+9(VVR)+0.5(TQmax)] was proposed; ROC analysis revealed a cutoff of 12 (AUC 0.96). An OABI of <12 was proposed for diagnosing OAB, 12-15 for equivocal and >15 for normal children. In the validation study OABI had 93 % sensitivity; 100 % specificity; 100 % positive predictive value & 94 % negative predictive value. The overall accuracy was 97 %.

Conclusion: While current diagnosis of OAB is mainly subjective, the proposed OABI is an objective way of diagnosing OAB using uroflow parameters. OABI may also help to assess treatment response. Further larger studies are warranted.

Keywords: Children; Diagnosis; Incontinence; Index; Over active bladder; Prognosis; Uroflow.