gms | German Medical Science

Background and current state of (inter)national research: Amyloidosis involves deposition of misfolded proteins that builds up in organs resulting in disfunctions. Transthyretin-related amyloidosis (ATTR) is caused by deposits of TTR, a transport protein for thyroxine and vitamin A produced by the liver. Depositions in the heart results in ATTR cardiomyopathy (ATTR-CM), a rare and progressive disease. The average survival time after diagnosis on symptomatic treatment is estimated to be 2–5 years [1]. A systematic literature review revealed the absence of information on the overall epidemiology of this condition in Germany.

Questions and objectives: A retrospective cohort study using German healthcare claims data was performed to assess the incidence of ATTR-CM. The methodology remained challenging for prevalence estimates: with no treatment option, rare specialized cardiologists and older age at diagnosis, prevalent patients are unlikely to consult on a regular basis for ATTR-CM and might remain uncaptured by a design requiring a yearly repeated diagnosis. Prevalent cases were simulated using a multistate model. Entry data for the simulation were the estimated number of incident cases and the mortality rate per year from the ATTR-ACT study [2] as the transition probability between states.

Methods or hypothesis: Since there is currently no Code in the International Classification of Diseases 10th Revision (ICD-10) for ATTR-CM in Germany, a proxy was created: a combination of ICD-10 for Amyloidosis and CM, considered in a time-dependent fashion. An Operation and Procedure (OPS) code was also required to exclude suspicious cases. The proportion of incident cases in the database was used to extrapolate the results to the adult German population. Survival times were then simulated for incident patients using a Markov multistate model. Incident and prevalent cases were summed up to assess yearly prevalence. The simulation was run over 50 years and repeated 500 times to get bootstrapped confidence intervals.

Results: Estimated incidence of ATTR-CM for the adult German population for 2017 was 328 [180; 551] cases. It took 27 simulation years to stabilize around 1920 patients currently in Germany.

Discussion: Even if the lack of proper IDC-10 for ATTR-CM adds uncertainty to the definition of cases, we were able to retrieve realistic estimates of incident cases. Plausible prevalence figures in line with the perception of KOLs were retrieved by simulation.

Practical implications: This original approach enabled to supplement the claims analysis when both the availability of the data and the characteristics of the disease lead to limitations that could not be alleviated otherwise.