External quality control results of urine dip-slide devices

Performance of a veterinary urine dipstick paddle system for diagnosis and identification of urinary tract infections in dogs and cats

OBJECTIVE

To evaluate the performance of a veterinary urine dipstick paddle (UDP) for diagnosis and identification of urinary tract infection (UTI) in dogs and cats.

DESIGN

Prospective, randomized, blinded study.

SAMPLE

207 urine specimens.

PROCEDURES

UDPs were inoculated by 2 investigators and incubated according to manufacturer's instructions. Results, including presence or absence of bacterial growth, organism counts, and identification of uropathogens, were compared between investigators and with microbiology laboratory results. A subset of UDPs with bacterial growth was submitted to the laboratory for confirmation.

RESULTS

The laboratory reported 64 (30.9%) specimens had growth of bacteria. Bacterial growth was reported for 63 (30.4%) and 58 (28.0%) of the UDPs by investigators 1 and 2, respectively. Sensitivity and specificity of the UDP for detection of bacterial growth were 97.3% and 98.6%, respectively, for investigator 1 and 89.1% and 99.3%, respectively, for investigator 2. For UPDs with ≥ 10(5) colony-forming units/mL, organism counts correlated well between the laboratory and investigators 1 (r = 0.95) and 2 (r = 0.89). Pathogen identification was not always accurate. Only 25 of 33 (75.8%) UDPs submitted for confirmation yielded bacteria consistent with those isolated from the original bacterial culture of urine.

CONCLUSIONS AND CLINICAL RELEVANCE

The veterinary UDP system was a sensitive test for screening patients for bacterial UTI, but uropathogen identification was not always accurate. When UDPs have bacterial growth, a fresh urine specimen should be submitted to the laboratory to confirm the identity of the organisms and to permit antimicrobial susceptibility testing.

Retrospective analysis of 55,769 HbA1c EQA results obtained from professional laboratories and medical offices participating in surveys organized by two European EQA centers over a nine-year period

External Quality Assessment (EQA) is an essential tool for laboratories to monitor the performances of their analyses. It also allows a comparison of methods and types of laboratories (professional laboratories vs. medical offices). We, therefore, compared 55,769 HbA1c EQA results obtained between 1999 and 2008 by laboratories participating in EQA schemes organized by two European centers, Switzerland (center 1) and France (center 2). We used simple, nonparametrical statistics suited to EQA results to calculate the yearly and global precision performances. All the results, including the outliers, were included in the calculations. The best global precision performances were obtained by professional laboratories and medical offices using DCA POCT devices, followed by professional laboratories with the Integra, Hitachi, Cobas Mira, and HPLC groups of devices, and finally by both types of laboratories with the NycoCard POCT devices. When considering yearly precision performances, an overall improvement over time was observed for almost all diagnostic devices of center 1, whereas the trend was less clear for center 2. The HbA1c EQA results collected and analyzed over a 9-year period showed that the DCA POCT devices used either by professional laboratories or medical offices had better reproducibility than laboratory devices (other than POCT) and that a general improvement of yearly precision performances was observed, especially when frequent EQA schemes were organized.

Retrospective analysis of 88,429 serum and urine glucose EQA results obtained from professional laboratories and medical offices participating in surveys organized by three European EQA centers between 1996 and 2007

BACKGROUND

The aim of this study was to provide inter-laboratory imprecision comparisons of different groups of diagnostic systems as well as a comparison of professional laboratories with medical offices performance on the basis of 88,429 glucose results obtained in external quality assessment (EQA) schemes organized by three European EQA centers between 1996 and 2007.

METHODS

A simple, non-parametrical statistical model suited to all EQA results, including outliers, was used to calculate yearly and global performance.

RESULTS

The best performance was obtained from professional laboratories with a group of three diagnostic systems--Hitachi, Integra, and Vitros, followed by Cobas Mira, and finally by Reflotron. For medical offices, the best performance was achieved with the Cobas Mira diagnostic systems, followed by the Reflotron, SpotChem, and Vitros DT60 diagnostic systems. A slight but overall improvement in performance over time was observed for most diagnostic devices.

CONCLUSIONS

The analysis of glucose EQA results collected over a 12-year period showed that professional laboratories obtained better performances than medical offices, and that a general improvement in yearly performance was observed for both types of laboratories.

Screening and treating asymptomatic bacteriuria in pregnancy

PURPOSE OF REVIEW

Asymptomatic bacteriuria (ASB) in pregnancy, if left undiagnosed and appropriately treated can lead to acute pyelonephritis in mothers and low birth weight in infants. Urine culture is the gold standard for diagnosing ASB. Unfortunately, urine culture is limitedly available. The present review aims at evaluating performance of various screening tests and effectiveness of antibiotic regimens for ASB.

RECENT FINDINGS

Positive dipslide test is very likely to have a definitive diagnosis of ASB, whereas a negative result effectively rules out ASB. Available evidences regarding the performance of urine dipstick are still conflicting, it is currently not appropriate to recommend urine dipstick for screening ASB in pregnancy. Choice of antibiotics should be guided by antimicrobial susceptibility testing whenever possible. Nitrofurantoin seems to be antibiotic of choice for ASB in pregnancy. Seven-day regimen of antibiotics gives a better microbiological cure rate but no difference in important clinical outcomes compared with 1-day regimen.

SUMMARY

Dipslide culture is a promising screening test for ASB. Pregnant women with ASB should be treated with 7-day regimen of antibiotics, although 1-day regimen might be appropriate in some settings. More research is needed for identifying appropriate screening tests for ASB.

Accuracy of diagnostic tests to detect asymptomatic bacteriuria during pregnancy

OBJECTIVE

A dipslide is a plastic paddle coated with agar that is attached to a plastic cap that screws onto a sterile plastic vial. Our objective was to estimate the diagnostic accuracy of the dipslide culture technique to detect asymptomatic bacteriuria during pregnancy and to evaluate the accuracy of nitrate and leucocyte esterase dipslides for screening.

METHODS

This was an ancillary study within a trial comparing single-day with 7-day therapy in treating asymptomatic bacteriuria. Clean-catch midstream samples were collected from pregnant women seeking routine care. Positive and negative likelihood ratios and sensitivity and specificity for the culture-based dipslide to detect and chemical dipsticks (nitrites, leukocyte esterase, or both) to screen were estimated using traditional urine culture as the "gold standard."

RESULTS

: A total of 3,048 eligible pregnant women were screened. The prevalence of asymptomatic bacteriuria was 15%, with Escherichia coli the most prevalent organism. The likelihood ratio for detecting asymptomatic bacteriuria with a positive dipslide test was 225 (95% confidence interval [CI] 113-449), increasing the probability of asymptomatic bacteriuria to 98%; the likelihood ratio for a negative dipslide test was 0.02 (95% CI 0.01-0.05), reducing the probability of bacteriuria to less than 1%. The positive likelihood ratio of leukocyte esterase and nitrite dipsticks (when both or either one was positive) was 6.95 (95% CI 5.80-8.33), increasing the probability of bacteriuria to only 54%; the negative likelihood ratio was 0.50 (95% CI 0.45-0.57), reducing the probability to 8%.

CONCLUSION

A pregnant woman with a positive dipslide test is very likely to have a definitive diagnosis of asymptomatic bacteriuria, whereas a negative result effectively rules out the presence of bacteriuria. Dipsticks that measure nitrites and leukocyte esterase have low sensitivity for use in screening for asymptomatic bacteriuria during gestation.

CLINICAL TRIAL REGISTRATION

ISRCTN, isrctn.org, 1196608

LEVEL OF EVIDENCE

II.

Difficulties for primary health care staff in interpreting bacterial findings on a device for simplified urinary culture

The reliability of interpretations of findings from dip-slide devices for culturing urine was investigated in a national Swedish external quality assessment (EQA) programme. Also investigated was the extent of improvement in the examination procedure achieved through personnel training programmes and information. According to Swedish national recommendations, dip-slide should only be used in primary health care (PHC) in cases of uncomplicated urinary tract infection (UTI) in females of childbearing age. The recommendations also define six possible outcomes of a dip-slide examination, outcomes that have formed the basis for the EQA programme since 2001. No improvement in ability to classify readings correctly into the six categories was noted for the period 2001 to 2006. Preparations containing 'mixed flora' presented participants with the greatest difficulty, with only 28 % correct reports. The EQA programme, with educational components and voluntary participation, has not improved quality. The disappointing results might be a reflection of the limited effort and resources allocated by clinical microbiology laboratories for training and for sustaining proficiency in the evaluation of dip-slides. For these reasons, we cannot at present recommend the dip-slide technique for use in PHC settings.