Factors associated with phlebotomy failure in an Alzheimer's Disease Research Center cohort

Venous blood collection through phlebotomy is critical for biomarker development and genetics research on Alzheimer's disease (AD) and related dementias. In this research setting, phlebotomy is often performed by clinical research coordinators (CRCs) rather than professional nurses or phlebotomists. Even though phlebotomy in older adults with cognitive impairment can be empirically challenging, data on the factors associated with phlebotomy failure in this special population are lacking. We addressed this question in the Massachusetts Alzheimer's Disease Research Center (MADRC) Longitudinal Cohort.

We applied mixed-effects logistic regression with phlebotomy failure as the dependent variable; age at visit, sex, education, body mass index (BMI), under-represented minority (URM) status, and Clinical Dementia Rating (CDR) scale global score as fixed effects; and participant ID as a random effect to account for multiple visits per participant.

Full data were available for a total of 1365 visits from 659 individual participants (average 2.1 visits/participant, range 1-7). Greater BMI (odds ratio [95% confidence interval]: 1.10 [1.05-1.16], P < 0.001) and CDR global score (1.51 [1.13-2.03], P = 0.005), but not age, sex, or education, were independently associated with higher odds of phlebotomy failure. URM participants had twice the odds of a phlebotomy failure compared to non-Hispanic Whites, although this trend did not reach statistical significance due to insufficient power (2.07 [0.97-4.41], P = 0.059).

Greater BMI and CDR as well as URM status are independently associated with higher odds of phlebotomy failure. Potential strategies to maximize participation of these subpopulations in biomarker and genetics research are discussed.