Health Care Analysis, Division of Society and Health, Linköping University, Sweden & The NEPI Foundation, Stockholm, Sweden.
Clinical Pharmacology, Pharmacy and Environmental Medicine, University of Southern Denmark, Odense, Denmark.
Basic Clin Pharmacol Toxicol. 2022 Jun;130(6):632-643. doi: 10.1111/bcpt.13727. Epub 2022 Apr 13.
The definition of a new case is a vital step in incidence studies in both epidemiology and pharmacoepidemiology, although with significant differences in methodology between the fields. We define and apply a framework for two different types of new cases of drug use, first-ever and recurrent, and show how the associated misclassifications related to length of run-in period can be expressed by the positive predictive value (PPV). In the study, we consider individual-level dispensations of statins 2006-2019 for 1,017,058 individuals with at least one dispensation in 2019 in Sweden. The incidence proportion for statins for both sexes of all ages in Sweden 2019 varied from 17.4/1000 with a run-in of 8 months, 9.45/1000 with 5 years and 8.4/1000 with 10 years. The PPV was 49% with 8 months and 89% for 5 years using 10 years as gold standard. We conclude that the interpretation of incidence and thus the selection of an appropriate run-in period, in pharmacoepidemiology, depends on whether first-ever use, recurrent treatment or both together (new cases) is the focus of the research question studied. At least five different misclassifications can be introduced depending on how incidence is defined.
新病例的定义是在流行病学和药物流行病学研究中发病率研究的重要步骤，尽管在这两个领域之间方法学存在显著差异。我们定义并应用了一种用于两种不同类型的新药物使用病例的框架，即首次和复发性，并且展示了与洗脱期长度相关的分类错误如何可以用阳性预测值 (PPV) 来表示。在这项研究中，我们考虑了瑞典 2006 年至 2019 年期间至少在 2019 年有一次配药的 1,017,058 名个体的他汀类药物个体配药情况。2019 年，瑞典所有年龄段的男女他汀类药物的发病率比例从 8 个月洗脱期时的 17.4/1000，变化到 5 年洗脱期时的 9.45/1000 和 10 年洗脱期时的 8.4/1000。使用 10 年洗脱期作为金标准，8 个月洗脱期的 PPV 为 49%，5 年洗脱期的 PPV 为 89%。我们得出结论，药物流行病学中的发病率的解释以及因此洗脱期的选择取决于研究问题的重点是首次使用、复发治疗还是两者都包括在内（新病例）。至少可以根据发病率的定义引入五种不同的分类错误。
