Diagnostic parameters of modified two-tier testing in European patients with early Lyme disease.

Modified two-tier testing (MTTT) for Lyme borreliosis (i.e. confirmation with an EIA instead of an immunoblot) has been shown to have improved sensitivity compared with standard two-tier testing (STTT) in samples from American patients, without losing specificity. The current study assesses the sensitivity and specificity of various algorithms of MTTT in European patients with erythema migrans (EM) as a model disease for early Lyme borreliosis, and in appropriate controls. Four different immunoassays were used in the first tier, followed by either an immunoblot or the C6-EIA, or were used as standalone single-tier test. These tests were performed on consecutively collected sera of 228 Dutch patients with physician-diagnosed EM in the setting of general practice, 231 controls from the general population, and 50 controls with potentially cross-reactive antibodies. All the variants of MTTT that were studied had significantly higher sensitivity compared with their equivalent STTT, while retaining comparable specificity. Within the MTTT algorithms, classifying equivocal results as positive yielded better diagnostic parameters than classifying equivocal results as negative. The best diagnostic parameters were found using the Enzygnost-2 assay in the first tier, followed by a C6-ELISA in the second tier (sensitivity 77.6%, 95% CI 71.7-82.9; specificity 96.1%, 95% CI 92.7-98.2). This algorithm performed significantly better than the equivalent STTT algorithm in terms of sensitivity (p < 0.001), while maintaining comparable specificity (population controls p = 0.617). Our results show that MTTT can be a useful tool for the serodiagnosis of European patients with early Lyme borreliosis.