Fig. 3

Influence of a change in test method on incorrect results (panel a) and technical failures (panel b). Eight hundred one individual participations were considered of which 323 participations were excluded because they were first participations for which no method information from the previous participation was available. Incorrect results include participations during which a false-negative or wrong mutation was reported. The evaluation of the effect of a switch in test method was evaluated on laboratory level for a given participation. Switching to a new methodology included both a switch of technique type (e.g. from a commercial test kit to NGS) as an upgrade to a higher version number for a given methodology, given that this might affect the detection limit and variants included in the test. Abbreviations: EQA, external quality assessment. Chi-squared tests or Fisher’s Exact tests (for cell counts below 5) were used to assess significance