Common Elements
The review process identified 1421 publications across four databases summarized by the PRISMA diagram in Figure 1. After removing duplicates (n=271) and records without abstracts (n=1062), 78 full-text articles were identified, of which 64 studies were excluded on the basis of their design, study population, or absence of a clear definition of altruism.
These eligibility criteria produced 14 studies (Table 1). All 14 studies investigated behaviors and attitudes toward clinical trial participation or tissue donation utilizing semi-structured interviews or questionnaires, including ten therapeutic clinical trials and four non-therapeutic tissue banking studies. Of the ten clinical trials, nine were Phase III randomized studies with one Phase I clinical trial.
Types of Altruism
Each study was condensed into summary statements describing concrete behaviors exhibited by study participants. Summary statements were then aligned according to the four subtypes of altruism in Table 2: pure altruism, weak altruism, reciprocal altruism, and hypothetical altruism.
Pure altruism described participant concern for the welfare of others and the investigators of the research study and embraced the moral value of helping others and society as a whole without expectation of medical or economic compensation. Reciprocal altruism, otherwise known as conditional altruism (Bidad et al),[9] combined the desire to help others with the expectation of personal benefit as a result of study participation, including potential indirect health benefits that might accrue during non-therapeutic studies. Weak altruism reflected the desire to return something of benefit to others and society as a whole but was not identified as the primary motivator for study participation. “Hypothetical” altruism described the stated, but untestable, the willingness of a study participant to accept assignment to the control arm of a randomized therapeutic clinical trial even though the eligibility criteria allowed that participant to withdraw and receive study drug.
Association Map
Examination of the summary statements revealed four defining features of participant behavior differentiating four subtypes of altruism (Table 3): expectations of personal benefit; benefit to others; social exchange, and impact on family/kinship. The resulting association map provides an objective basis to distinguish participant behaviors in future studies. Characteristics of personal benefit included: positive impact on disease prognosis, restoration of hope, or financial compensation. Benefit to others included measurable gain for other patients and/or medical staff. Social exchange was defined as the participant’s intent to benefit the medical staff and contribute to generalized scientific knowledge. Care for the medical staff, investigators, and the hospital was therefore common to both “benefit to others” and “social exchange.” Kinship reflected consideration for family members as the reason for altruistic behaviors.
Characteristic Features
Pure altruism and reciprocal altruism were most commonly identified during this systematic review (9 studies; 64%), followed by weak altruism in three (21%), and “hypothetical” altruism in one (7%) study. Pure altruism was not associated with self-interest or benefit to kinship but was strongly associated with benefit to others and the medical staff as well as social exchange by contributing to scientific knowledge. Like pure altruism, weak altruism was not associated with expectation of personal benefit. However, weak altruism differed from pure altruism in expectation of benefits for family members and advancement of scientific knowledge. Reciprocal altruism demonstrated a moderate correlation with benefit to others and scientific knowledge but exhibited expectations of personal benefit as well as benefit to kinship. Unlike the other types of altruism, the existence of “hypothetical” altruism cannot be tested through experimental observation.