- Detailed legend: Diagnostic accuracy of mid-stream-clean-catch samples vs. urethral catheterization/suprapubic puncture. 95 % confidence intervals in brackets. A cut-off of ≥ 104 cfu/ml has been chosen in the study by Mabeck. TP True positives; TN True negatives; FN False negatives; FP False positives; PPV Positive predictive value; NPV Negative predictive value; SEN Sensitivity; SPE Specificity