Non-oncological drug-induced blood disorders: a cost of illness study using the microcosting Methodology - study plan [protocol]

Drug-induced disorder „can result from unanticipated or anticipated drug effects“ (1). The prevalence of hematological adverse drug reactions (ADR) in chemotherapeutics is expected to be high; for non-chemotherapeutics, there is insufficient epidemiological data, although a spontaneous reporting system is mandatory in a drug's life cycle (2-6). ADR is considered to be the fifth cause of death, with the hospitalization rate caused by ADR estimated to be between 0.9-7.9% (7-8), while one study suggests that about „10 to 20% of hospitalized patients will experience ADRs during their stay“ (9). Frequency data on hospital admissions due to hematological ADR vary between studies, e.g., 9% (7) up to 26.5% (10). The study by Abu et al. categorized major ADR types based on system disorders, where hematologic ADR encountered 9.9-15.2% of ADRs (9). The same study estimated costs per ADR from 65.00 to 12,129.90 USD, whereas costs were generally lower when the micro- costing approach was used (9). A cost-of-illness (COI) study should be performed to precisely determine the costs generated by ADR. COI studies measure the economic burden of an illness on society, health insurance funds, or patients. Jefferson et al. (2000) defined “the aim of COI studies is descriptive: to itemize, value, and sum the costs of a particular problem with the aim of giving an idea of its economic burden“ (11). There are different methods of conducting this type of study, such as prevalence‐based, incidence‐based, or econometric approaches, with again different approaches (e.g., prospective, retrospective; top-down, bottom-up…) or with different perspectives of COI studies (such as societal, health care system, third-party payer) (11). However, micro-costing studies represent the gold standard for conducting COI studies (12). Only a few cost drivers of HADR have been proven to date, e.g., prolonged in-hospital stay, costs of using drugs, and transfusion costs (13-14).STUDY PLA