Within early benefit assessment of pharmaceuticals in Germany, addenda can be commissioned by the Federal Joint Committee (FJC) to the health technology assessment (HTA) agency, mainly as a result of a hearing. Our aim was to analyze the issues for and impact of commissioned addenda, as well as the agreement between HTA agency recommendations and FJC decisions.

All available relevant documents on addenda commissioned up to the end of 2017 were screened and their essential content extracted. Differences between the HTA agency and FJC recommendations were tested, and concordance was analyzed using agreement statistics (Cohen's kappa and Fleiss’ kappa).

Most of the 90 addenda commissioned up to the end of 2017 concerned oncological products. In all contingent comparisons, positive changes in added benefit or evidence level on a subpopulation basis (n = 124) were more common than negative changes. Agreement of assessments, addenda, and appraisals reached a moderate strength for added benefit (Fleiss’ kappa 0.47, range 0.41 - 0.54). Overall agreement between addenda and appraisals on a binary nominal basis was poor for added benefit (Cohen's kappa 0.18, range 0.01 - 0.36) and fair for evidence quality (Cohen's kappa 0.35, 0.19–0.52). Cohen's kappa ranged from “less than by chance” (respiratory diseases) to “perfect” (neurological diseases), but was only statistically significant for neurological and other diseases. Three addenda are presented in detail as examples.

Addenda have a high impact on decision-makers’ appraisals, offering additional analyses of supplementary evidence submitted by the manufacturers. Nevertheless, the agreement between addenda and appraisals varies, highlighting different methodological approaches and decision-making factors between the HTA agency and the FJC.