Aims: To evaluate the IRIS flow microscope for the examination of urine specimens and to compare its performance with that of manual methods; in addition, to assess its usefulness as a screening system for the detection of significant bacteriuria in a routine clinical laboratory. Methods: The IRIS system was compared with manual quantitative microscopy for the detection of formed elements and with a variety of culture methods to detect urinary tract infection. Results: The IRIS had a higher sensitivity for the detection of clinically significant formed elements than did manual methods, and using a combination of bacterial and white cell counts produced a sensitivity and specificity of 94.9% and 54.4%, respectively, for predicting positive significant growth, with a 98.5% predictive value for a negative result. Approximately 50% of specimens could be reported as negative on the day of receipt using the screening algorithm. Conclusions: The sensitivity and specificity of the IRIS is equivalent to that of other automated screening systems and would remove the need for manual microscopy for most specimens. The system was easy to operate and is a useful addition to the methods currently available for the examination of urine specimens. U rinary tract infection (UTI) is one of the most common infections diagnosed in clinical microbiology laboratories. Bacteriuria has an important role in disease throughout life. Damage caused by combined reflux and infection is most likely to occur in the first year of life, during the crucial period of renal growth, resulting in cortical damage and scarring, which may lead to renal failure later in life, and 50% of women will have at least one episode of UTI. Urine specimens account for approximately one third of all specimens received in our laboratory, and approximately 80% of these prove to be negative on culture. Numerous methods to screen for bacteriuria have been described previously, 1 and automated systems have been developed to screen routine urine specimens, although few have gained widespread acceptance.
2The IRIS 939 UDx (manufactured by International Remote Imaging Systems, Chatsworth, Los Angeles, California and distributed in the UK by Launch Diagnostics Limited, Ash House, New Ash Green, Longfield, Kent) consists of a flow microscope and associated software capable of analysing captured images to identify and quantify formed elements and bacteria in urine.''Urine specimens account for approximately one third of all specimens received in our laboratory, and approximately 80% of these prove to be negative on culture''The IRIS system has been available in the USA for several years.3 The earlier versions classified particles by size alone and required the captured images to be verified by the operator. This latest edition has powerful image analysis software that is capable of identifying the following formed elements:N erythrocytes (RBC) N leucocytes (WBC) N leucocyte clumps (WBC clumps) N bacteria (BACT) N yeasts N squamous, transitional, and renal epithelial cells
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