A 65-year-old man comes to the clinic for follow-up treatment of hypertension. He is on 2 antihypertensive agents and says he is compliant with his medication regimen. The patient has no other medical problems. Blood pressure is 134/88 mm Hg and pulse is 78/min and regular. BMI is 32 kg/m². Physical examination is otherwise unremarkable. His fasting blood glucose levels on 2 recent laboratory workups were 108 mg/dL and 111 mg/dL. He is concerned about his risk of dementia because his father suffers from Alzheimer dementia. After excluding from the analysis participants with diabetes who had an unusual clinical course such as high fluctuations in reported glucose levels, the investigators repeat their calculations of the hazard ratio of dementia. This analytical step is best referred to as which of the following?

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Explanation: Sensitivity analysis refers to repeating primary analysis calculations after modifying certain criteria or variable ranges; the goal is to determine whether such modifications significantly affect the results initially obtained. With any study, a number of decisions are made based on certain assumptions or by consensus (eg, choosing 5-year rolling windows as opposed to 2- or 8-year rolling windows). If results of sensitivity analyses conducted with slight changes in certain variables (eg, changing rolling window period, changing cutoffs for average glucose levels by ±10%) are similar to the initial results, the investigators can be more confident of the robustness of their results. In this case, patients with diabetes who had high fluctuations in glucose levels were excluded. If, on repeat analysis excluding those patients, the p-value for the association between average glucose levels and dementia remains statistically significant among the remaining patients with diabetes, this would further confirm the investigators' conclusions as it would make it less likely that high fluctuations in glucose levels explain the different hazard ratios obtained. (Choice A) Participants can be blinded so that they are unaware of which intervention they are receiving; observers/investigators can be blinded so that they are unaware of which intervention the participants are receiving. Blinding protects against bias that could favor one study arm if participants or observers/investigators were aware of the intervention. Unlike sensitivity analysis, blinding is part of initial study design rather than analysis. (Choice B) Linear regression models the linear relationship between a dependent variable and one or more independent variables. For example, multiple linear regression could be used to quantify the effects of alcohol use, tobacco smoking, and charred food consumption (independent variables) on the incidence of gastric cancer (dependent variable). (Choices C and D) Propensity scoring typically weighs different variables (eg, severity of different comorbidities) in both the treatment and the control groups to ensure that these variables are balanced between both groups. An individual in the treatment group can be matched with an individual in the control group who has a similar propensity score. Matching can also be conducted based on similar variables (eg, age, sex) even in the absence of propensity scoring. Educational objective: Sensitivity analysis refers to repeating primary analysis calculations in a study by modifying certain criteria or variable ranges to determine whether such modifications significantly affect the results initially obtained. References: A tutorial on sensitivity analyses in clinical trials: the what, why, when and how. (http://www.ncbi.nlm.nih.gov/pubmed/23855337)

A 65-Year-Old Man Comes to the Clinic for Follow-Up Treatment