Screening out non-infected urine samples.

38 Chronic fatigue syndrome Sean Lynch, et al. 39 Patient satisfaction and style of practice Domhnall Macauley 40 Reflotron measurement of blood cholesterol F A Majeed 40 Reaccreditation of GPs Philip Schuppler 40 Audit in general practice A 0 Baird 41 Surgical simulation for general practitioners N K Menon 41 Appliance for hemiplegic patients J Brims, et al. 41 Note to authors of letters: Please note that all letters submitted for publication should be typed with double spacing. Failure to comply with this may lead to delay in publication. Screening out non-infected urine samples Sir, Hiscoke and colleagues recommended that clear urine samples with negative strip tests for blood, protein and nitrite do not require laboratory culture as the predictive value of these tests for the absence of bacteriuria was 98.5%.' We tested 282 consecutive urine samples Over a five month period, assessing appearance and testing with N-labstix® (Ames) for protein, blood and nitrite, before sending for laboratory culture. Of the 282 samples 82 (29.1%) were assessed as clear in appearance and gave negative strip results, and 78 of these negative specimens were shown not to have significant bacteriuria, giving a predictive value for the absence of bacteriuria in these samples of 95.1%. Significant bacteriuria was found in 65 (23.0%) of the 282 samples. We have therefore confirmed the value of the method of screening out non-infected urine samples but would like to comment further on one aspect of the method which may cause difficulties to those using it. Assessment of urine appearance as 'clear' or 'turbid' is subjective and we soon became aware that some samples fell into a doubtful category. We analysed this by comparing practice and laboratory assessment of urine clarity. Testers were asked to assess as 'clear' only those specimens in which there was no sign of turbidity, sediment or debris. Laboratory assessment was made about three hours after the practice assessment. A total of 267 specimens were compared. In 57 of the 267 specimens (21.3%) there was disagreement between the practice and laboratory. Either the appearance of these samples changed in the time between tests or there was difficulty in judging the clarity of the sample. However, only one of these samples showed significant bacteriuria. We therefore conclude that testing for clarity is practical and valid and while recommending that testers should be strict in the assessment of clarity, there appears to be a safety …