Clinical evaluation of the slide centrifuge (cytospin) gram's stained smear for the detection of bacteriuria and comparison with the FiltraCheck-UTI and UTIscreen

Comparison of the reliability of Gram-negative and Gram-positive flags of the Sysmex UF-5000 with manual Gram stain and urine culture results

OBJECTIVES

Recently, the fully automated flow cytometry-based UF-5000 (Sysmex Corboration, Kobe, Japan) urine sediment analyzer was developed providing bacteria (BACT) info flags for more accurate bacterial discrimination of urinary tract infections (UTIs). This study aimed to compare the reliability of the UF-5000 BACT-info flags with manual Gram stain and urine culture as the gold standard method.

METHODS

A total of 344 urine samples were analyzed on the UF-5000 and compared with manual microscopic Gram stain and urine cultures. Agreement was assessed by Cohen's kappa (κ) analysis. The Youden index was used to determine the optimal BACT and white blood cell (WBC) cut-off points for discriminating positive and negative urine cultures.

RESULTS

Overall 98/344 (28.5%) samples were urine culture positive at a cut-off of ≥105 CFU/mL. "Gram-negative?" UF-5000 BACT-Info flags showed a better concordance of 25/40 (62.5%) with urine culture compared to Gram stain with 30/50 (60%). The results for UF-5000 discrimination of Gram-positive and Gram-negative microorganisms demonstrated a substantial (κ = 0.78) and fair (κ = 0.40) agreement with urine culture. Optimal cut-off points detecting positive urine cultures were 135 BACT/µL (sensitivity [SE]: 92.1%, specificity [SP]: 85.4%, positive predictive value [PPV]: 71%, negative predictive value [NPV]: 96%) and 23 WBC/µL (SE: 73.5%, SP: 84.1%, PPV: 65%, NPV: 89%).

CONCLUSIONS

The UF-5000 analyzer (Sysmex) is a reliable diagnostic tool for UTI screening. The displayed BACT-Info flags allow a quick diagnostic orientation for the clinician. However, the authors suggest verifying the automated Gram categories with urine culture.

Current and developing technologies for monitoring agents of bioterrorism and biowarfare

Recent events have made public health officials acutely aware of the importance of rapidly and accurately detecting acts of bioterrorism. Because bioterrorism is difficult to predict or prevent, reliable platforms to rapidly detect and identify biothreat agents are important to minimize the spread of these agents and to protect the public health. These platforms must not only be sensitive and specific, but must also be able to accurately detect a variety of pathogens, including modified or previously uncharacterized agents, directly from complex sample matrices. Various commercial tests utilizing biochemical, immunological, nucleic acid, and bioluminescence procedures are currently available to identify biological threat agents. Newer tests have also been developed to identify such agents using aptamers, biochips, evanescent wave biosensors, cantilevers, living cells, and other innovative technologies. This review describes these current and developing technologies and considers challenges to rapid, accurate detection of biothreat agents. Although there is no ideal platform, many of these technologies have proved invaluable for the detection and identification of biothreat agents.

Evaluation of a rapid bacterial ATP assay for screening BAL samples from ICU patients submitted for quantitative bacterial cultures

A novel application of a rapid diagnostic technique for the detection of significant bacterial pathogens (>/=10(4) cfu/mL) in bronchoalveolar lavage (BAL) samples from critically ill ventilated patients is described. This rapid diagnostic assay (UTIscreen, Coral Biotechnology, San Diego, CA) utilizes a luciferin-luciferase reaction to detect bacterial adenosine triphosphate (ATP) and is currently commercially available for screening bacteriuria in urine specimens. One hundred and twenty-eight BAL samples were examined microscopically with Gram's stain and tested in parallel using the bacterial ATP assay and standard quantitative culture. The sensitivity (Sn), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV) for the detection of bacteria >/=10(4) cfu/ml in BAL specimens for the bacterial ATP assay was 87%, 59%, 39%, and 94%, and for the Gram's stain was 73%, 65%, 39%, and 89%, respectively. The diagnostic utility was improved by combining the results of Gram's stain/bacterial ATP assay results with Sn, Sp, PPV, and NPV of 97%, 38%, 32%, and 97% respectively. A combined negative rapid test consisting of Gram's stain/bacterial ATP assay rules out significant bacteria in BAL samples with a high degree of certainty. Future studies are needed to clinically validate these observations.