More laboratory testing: greater cost but not necessarily better

Area of Science:

• Clinical Microbiology
• Diagnostic Assay Evaluation
• Pediatric Infectious Diseases

Background:

• Bacterial latex agglutination assay is commonly used for pediatric patients to screen for bacterial antigens in cerebrospinal fluid (CSF) and urine.
• Concerns regarding the assay's accuracy and high cost prompted a review of its clinical utility.
• Previous literature has raised questions about the reliability of bacterial antigen testing.

Purpose of the Study:

• To retrospectively evaluate the accuracy, clinical impact, and cost-effectiveness of the bacterial latex agglutination assay.
• To assess the sensitivity and specificity of the assay in urine and CSF specimens.
• To determine if the assay influences patient treatment or hospital course.

Main Methods:

• Retrospective review of 6,370 bacterial latex agglutination tests performed between May 1995 and November 1996.
• Analysis of patient charts to correlate test results with clinical outcomes.
• Evaluation of assay sensitivity, specificity, false positive, and false negative rates.

Main Results:

• Sensitivity and specificity were 28.6% and 86.7% for urine, and 70.0% and 99.4% for CSF.
• The assay generated 13 false negatives and 59 false positives.
• Annual billed costs averaged $167,000, excluding indirect costs from unnecessary treatments and prolonged hospital stays.

Conclusions:

• Bacterial antigen latex agglutination testing lacks sufficient sensitivity and specificity for reliable screening.
• Accurate results showed no clinical impact, while inaccurate results led to unnecessary patient management and significant costs.
• The continued use of this assay should be reconsidered due to its questionable clinical efficiency and high financial burden.