Can urine dipstick testing for urinary tract infection at point of care reduce laboratory workload?

Abstract

Aim: The University Hospitals of Leicester NHS Trust microbiology laboratory receives 150 000 urine samples each year, approximately 80% of which prove to be culture negative. The aim of this study was to reduce the proportion of culture negative urines arriving in the laboratory, by producing local evidence based guidelines for the use of urine dipstick testing at point of care within the trust's three acute hospitals. Methods: One thousand and seventy six unborated urine samples were dipstick tested at the point of care using an automatic strip reader. Quantitative results for the four infection associated markers-leucocyte esterase, nitrite, blood, and protein-were compared with the results of conventional laboratory microscopy and culture. Results: The performance of different marker combinations was calculated against the routine laboratory methods. One hundred and seventy five (16.3%) samples were negative for all four markers. Of these dipstick negative samples, only three (1.7% of all true positives) were positive by culture. The absence of all four infection associated markers was found to have a greater than 98% negative predictive value and a sensitivity and specificity of 98.3% and 19.2%, respectively. Conclusions: A urinary dipstick testing algorithm for infection associated markers was derived for use in hospital patients to screen out negative urines. Two years after distributing the algorithm and promoting access to reagent strips and strip readers, a reduction in the urine workload has been seen against an otherwise increasing laboratory specimen load. U rinary tract infection (UTI) is one of the most common clinical conditions in both hospital and the community. Almost a third of all specimens sent to our laboratory are requests for the investigation of possible UTI. Of a total of 150 000 urine samples received each year, approximately one third originate from within the hospital trust. Overall, 80% of urine samples are found to be negative for bacteriuria. Laboratory resources and patient care could be improved by the appropriate use of a validated near patient test for UTI.''Almost a third of all specimens sent to our laboratory are requests for the investigation of possible urinary tract infection''The role of biochemical markers in screening for urinary tract infections in the near patient setting is well established.1 2 Studies have concluded that near patient urine dipstick testing (NPUDT) is a more accurate method for diagnosing UTI than clinical assessment on its own.3 In addition, NPUDT is better at excluding UTI when the results are negative than confirming a diagnosis of UTI when they are positive. 4 This methodology is also simple and relatively inexpensive. The four infection associated biochemical markers have been shown to have a negative predictive value of 97-99%.

Evaluation of the Alfred 60/AST Device as a Screening Test for Urinary Tract Infections

“…It is therefore not surprising that urine samples constitute the largest proportion of specimens tested in microbiology laboratories (2,3).…”

“…rinary tract infections (UTIs) are one of the most common infections diagnosed in community and hospital settings (1,2). It is therefore not surprising that urine samples constitute the largest proportion of specimens tested in microbiology laboratories (2,3).…”

“…Considering that 70 to 80% of urine samples are proven negative for UTI (2,4,5,6,7), a rapid screening method could reduce costs and turnaround times. Alternative methods based on chemical and flow cytometry have had mixed results (2,4,8). This study was designed to evaluate the utility of a fully automated bacterial culture device (Alfred 60/AST) which utilizes laser nephelometry to detect and quantify growth (CFU/ml) (9).…”

Multistix 10 SG Leukocyte Esterage Dipstick Testing in Rapid Bedside Diagnosis of Spontaneous Bacterial Peritonitis: A Prospective Study

“…5,6 The reagent strips detecting leukocyte esterase activity in biological fluids have been validated for the diagnosis of urinary tract infections, meningitis, and pleural infections. [7][8][9] Aim of the study was to determine the sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV), and accuracy of leukocyte esterase reagent strips (LERS) for the diagnosis of SBP in cirrhotic patients with ascites.…”

Evaluation of leukocyte esterase and nitrite strip tests to detect spontaneous bacterial peritonitis in cirrhotic patients

“…Intriguingly, reagent strips detecting leukocyte esterase activity in biological fluids have been validated for the diagnosis of urinary tract infections [9,10] , peritonitis in patients on continuous ambulatory peritoneal dialysis [11] , pleural infections [12] and meningitis [13] . The observation that nitrate levels in ascites fluid are raised in patients with SBP is also of interest [14] .…”