Quality of Lyme disease serology. Lessons from the German Proficiency Testing Program 1999-2001. A preliminary report

External quality control surveys are an important tool in regulating the quality of infection serology in general and of borreliosis serology in particular. We report on the results of a Lyme disease proficiency testing program which is regularly organised twice a year by our institutions in close cooperation with the Institute of Standardisation in the Medical Laboratory (INSTAND).

From 1999 to 2001, between 226 and 337 microbiological laboratories participated in each of the four surveys that have been held so far. In addition, between 23 and 30 laboratories from 13 other European countries also participated in each trial. In each survey two serum samples which had been unambiguously characterised by six reference laboratories to contain or not to contain antibodies against the Lyme disease spirochete were distributed in order to determine the accuracy of the diagnostic methods used in participating laboratories. The laboratories also reported interpretative statements of whether or not the test constellation suggested a possible borrelial infection and if an early or late phase of the specific antibody response was suspected.

Test results were found to be in part highly variable and clearly correlated with the manufacturers and the applied test methodology. It was also clear that IgM tests were more difficult to handle than were IgG tests. ELISA-testing was more reproducible and proved to be more sensitive and specific than IFA and IHA testing. Quantification of test results and reporting of specific immunoblot bands also showed high variability. Moreover, for some assays a high number of false positive and false negative test results were reported by the participants.

In view of our results further standardisation of Lyme disease serology is not just desirable but is urgently needed. Moreover, stronger criteria for the validation of available test kits must be applied.