Counterpoint: the treatment decision design

Abstract

The comparative new-user design is a principled approach to learning about the relative risks and benefits of starting different treatments in patients who have no history of use of the treatments being studied. Vandenbroucke and Pearce (Am J Epidemiol. 2015;182(10):826-833) discuss some problems inherent in incident exposure designs and argue that epidemiology may be harmed by a rigid requirement that follow-up can only begin at first exposure. In the present counterpoint article, a range of problems in pharmacoepidemiology that do not necessarily require that observation begin at first exposure are discussed. For example, among patients who are past or current users of a medication, we might want to know whether treatment should be augmented, switched, restarted, or discontinued. To answer these questions, a generalization of the new-user design, the treatment decision design, which identifies cohorts anchored at times when treatment decisions are being made, such as the evaluation of laboratory parameters, is discussed. The design aims to provide estimates that are directly relevant to physicians and patients, helping them to better understand the risks and benefits of the different treatment choices that they are considering.

Keywords: pharmacoepidemiology; study design.

Figure 1.

Design schematic of a nonexperimental iron dose-ranging study.

Figure 2.

Design schematic of a nonexperimental study of oral antidiabetic treatment intensification. HbA1c, hemoglobin A1c.

Figure 3.

Design schematic of a nonexperimental study of perioperative statin use.

Figure 4.

Design schematic of a nonexperimental analogue of a randomized withdrawal study of diuretics among patients starting hemodialysis.