OBJECTIVES: To compare the results of the Blaivas and Groutz nomogram in the diagnosis of female urinary obstruction with videourodynamic tests.METHODS: We performed a transverse study in aseries of 52 female patients with ages between 20 and 81 years (mean age: 48.7 years; standard deviation: 14.4 years) and functional lower urinary tract symptoms referred for videourodynamic studies. All patientsunderwent free flowmetry and voiding videourodynamic study. From the scores of free flowmetry and maximum detrusor pressure in the detrusor pressure/voiding flow test of the urodynamic study they were classified in one offour categories following the Blaivas and Groutz nomogram. Following urodynamic data they were classified into three categories: absence of obstruction, bladder neck obstruction and urethral obstruction.The nomogram results were compared with the videouro-dynamic data using the Pearson chi-square statistical test. The diagnostic sensitivity and specificity of the nomogram were also determined.RESULTS: The Blaivas and Groutz nomogram showed a significant association with the videourodynamic data (p = 0.000). Its diagnostic sensitivity for obstruction was 100%, but its specificity was only 67.5%. The percentage of diagnostic discrepancies was maximal in the mild obstruction, where one third of the patients were obstructed following the videourodynamic data.CONCLUSIONS: The Blaivas and Groutz nomogram is a sensitive method for the diagnosis of obstruction, but its specificity is low so that it has the tendency to overdiagnose the presence of obstruction in the female patient