Selection bias in a study of implantable defibrillator patients: the role of Type D personality.
BACKGROUND
Selection bias constitutes a major issue in research using volunteers as study participants.


OBJECTIVE
We examined whether research in partners may affect participation rates of implantable cardioverter-defibrillator (ICD) patients with a Type D personality (joint presence of negative affectivity and social inhibition).


METHODS
Patients who underwent ICD implantation between May 2003 and November 2007, and who had a partner, were included (n = 440). In September 2005, a substudy on partners of ICD patients was added (n = 276 patients).


RESULTS
The proportion Type D patients after the start of the partner substudy was significantly lower as compared to the proportion before this substudy (17.5% versus 28.8%; p = 0.006). Patients who participated following the start of the partner substudy were less likely to have a Type D personality (OR = 0.44; p = 0.002), adjusting for possible confounders. In the partner substudy, nonparticipation was more prevalent among partners of Type D patients as compared to partners of non-Type D patients (20.4% versus 10.1%; p = 0.044). Partner nonparticipation was marginally significantly associated with Type D personality of the patient (OR = 2.13; p = 0.083), adjusting for confounders.


CONCLUSIONS
The addition of a partner substudy may be related to a decreased proportion of participants with a Type D personality. Nonparticipation was more prevalent among partners of Type D patients. These observations may influence results of studies, as Type Ds tend to be less healthy.
van den Broek
Krista C
KC
CoRPS-Center of Research on Psychology in Somatic Diseases, Department of Medical Psychology, Tilburg University, Tilburg, The Netherlands. CvdBroek@uvt.nl
Nyklíček
Ivan
I
Denollet
Johan
J
D000293:Adolescent; D000328:Adult; D000339:Affect; D000368:Aged; D000369:Aged, 80 and over; D001007:Anxiety / Q000523:psychology; D017147:Defibrillators, Implantable / Q000523:psychology*; D003863:Depression / Q000523:psychology; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D010551:Personality / Q000502:physiology*; D015983:Selection Bias