Screening urine samples for the absence of urinary tract infection using the sediMAX automated microscopy analyser

Abstract

Urinalysis culminates in a workload skew within the clinical microbiology laboratory. Routine processing involves screening via manual microscopy or biochemical dipstick measurement, followed by culture for each sample. Despite this, as many as 80 % of specimens are reported as negative; thus, there is vast wastage of resources and time, as well as delayed turnaround time of results as numerous negative cultures fulfil their required incubation time. Automation provides the potential for streamlining sample screening by efficiently (.30 % sample exclusion) and reliably [negative predictive value (NPV) ¢95 %] ruling out those likely to be negative, whilst also reducing resource usage and hands-on time. The present study explored this idea by using the sediMAX automated microscopy urinalysis platform. We prospectively collected and processed 1411 non-selected samples directly after routine laboratory processing. The results from this study showed multiple optimum cut-off values for microscopy. However, although optimum cut-off values permitted rule-out of 40.1 % of specimens, an associated 87.5 % NPV was lower than the acceptable limit of 95 %. Sensitivity and specificity of leukocytes and bacteria in determining urinary tract infection was assessed by receiver operator characteristic curves with area under the curve values found to be 0.697 [95 % confidence interval (CI): 0.665-0.729] and 0.587 (95 % CI: 0.551-0.623), respectively. We suggested that the sediMAX was not suitable for use as a rule-out screen prior to culture and further validation work must be carried out before routine use of the analyser.

Accuracy of Dongjui analyzer for reducing the number of unnecessary urine cultures in an outpatient setting

“…In our study, we found that the bacteriuria parameter of the Dongjui DJ-8602 urine sediment analyzer, which uses an image analysis method has poor discriminatory power for UTI. Our results are consistent with other studies that the bacteriuria parameter with automated microscopy cannot be used alone to reduce the number of negative urine culture samples [17][18][19][20].…”

Using artificial intelligence to reduce diagnostic workload without compromising detection of urinary tract infections

“…Additionally, greater than 50% of samples in the study by Inigo et al originated from inpatients and both studies included specimens from catheterised patients [3, 4]. In contrast to those findings, Sterry-Blunt et al [6] reported from a study of 1411 samples that the highest achievable negative predictive value when using white blood cell and bacterial count thresholds was 89·1% and concluded that the SediMAX should not be used as a screening method prior to culture.…”

“…To our knowledge, there are no other observational studies of this magnitude for the study of urine analysis for the diagnosis of UTIs. Most previous studies with the objective of predicting urine culture based on variables generated from sediment analysis, flow cytometry, and/or dip-stick testing have been controlled studies of a few hundred patients, with little consistency in the inclusion criteria [3, 4, 6, 13, 27–29]. Prior efforts to establish a heuristic model based on microscopy thresholds generated conflicting results.…”

Direct Identification of Urinary Tract Pathogens from Urine Samples, Combining Urine Screening Methods and Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

“…Urine culture is still the gold standard for the microbiological confirmation of UTIs; however, it takes 24 to 48 h to provide results. The use of screening methods, such as traditional Gram staining or other methods for counting urine particles, like flow cytometry or automated microscopic urine sediment analysis, allow the prompt prediction of negative samples and a preliminary identification of microorganisms in positive samples (4)(5)(6)(7). Nevertheless, this information obtained from these methods is insufficient and requires culture and other biochemical tests.…”