Despite previous low levels of Māori participation in clinical trials, equal numbers of Māori and non-Māori participants were recruited in this study among patients at high risk of CVD. The trial will therefore be able to assess the consistency of the effects of the polypill in Māori compared with non-Māori, though it is not adequately powered to separately assess these effects in Māori and non-Māori.
The two key aspects to achieving the recruitment target were supporting indigenous self-determination and making equal recruitment a priority. Indigenous self-determination was supported by: having experienced Māori researchers in trial governance; employment of Māori research nurses or research nurses with significant experience working with Māori; and ensuring that contact with participants was culturally appropriate. Equal recruitment was prioritised by: having a commitment to this by the trial Steering Committee; obtaining sufficient extra funding for additional research nurse time required to recruit Māori; targeting practices with high Māori populations; over-sampling and broadening the search strategy to identify potentially eligible Māori; and extending recruitment duration for Māori. It is also likely that perceived acceptability of the polypill to Māori contributed to recruitment onto the trial.
Once Māori were identified as potentially eligible from electronic practice records, they were statistically significantly more likely than non-Māori to proceed to each subsequent stage of recruitment. Māori were also more likely than non-Māori to be excluded once their consent had been obtained, primarily due to the greater proportion of Māori with a CVD risk that was too low for inclusion. This is most likely because of the broader search strategy used to identify potentially eligible Māori (Table 2). Māori may have been more likely than non-Māori to have no or incomplete laboratory results because they were younger and less likely to have a history of coronary artery disease. If research nurses (or other research staff) had obtained laboratory specimens directly (rather than requiring patients to attend a community laboratory), the trial may have been even more accessible to Māori.
Higher triglyceride levels may explain why Māori were more likely than non-Māori to be excluded because in these circumstances LDL is unable to be calculated. The differences in baseline characteristics between randomized Māori and non-Māori are also likely to reflect the broader search strategy used to identify potentially eligible Māori, plus the greater prevalence of type 2 diabetes among Māori .
The differences between Māori and non-Māori do not undermine the validity of the comparison between treatment groups (polypill-based care or usual care) because participants are randomly allocated to treatment groups. However, these differences will need to be taken into consideration when interpreting any differences in treatment effect in Māori and non-Māori.
While the trial has oversampled Māori, people from the other major ethnic groups in the NZ population (Pacific, Asian, European and Other) have also been included. The proportion of Pacific people in the trial is greater than in the general population (9 vs 6% ). This is most likely because practices that were targeted by the trial for their high Māori enrollment also had high enrollment of Pacific people.
Self-reported adherence to quadruple therapy was lower among Māori than non-Māori but this difference became statistically non-significant when we stratified participants by history of CVD, suggesting it is likely to be at least partially due to the higher prevalence of CVD amongst non-Māori participants in the trial.