Evaluation of Lyme serologic quantitative test indexes: High first-tier test index values predict positive second-tier result in standard and modified 2-tier Lyme testing algorithms.

OBJECTIVES

In this study, we evaluated the potential utility of reporting a quantitative Lyme serologic test index to improve the utility of results from first-tier Lyme assays.

METHODS

Serum from consecutive samples sent to our laboratory for Lyme testing were tested on 2 commercial first-tier Lyme assays and evaluated to determine the probability of second-tier confirmation based on the serologic index value.

RESULTS

For both assays, we identified an index value above which 100% of samples confirmed on second-tier testing using both standard and modified 2-tier testing algorithms. Lower rates of confirmation were observed for positive or equivocal samples with lower index values.

CONCLUSION

The use of a Lyme test index value may eliminate the need for confirmatory testing on many positive first-tier samples, providing more rapid turnaround time to a definitive result. This practice would also increase efficiency in the clinical laboratory.