To our knowledge, this is the first study evaluating rates and determinants of adherence to secondary antibiotic prophylaxis for ARF recurrence in New Caledonia. Our study showed that there were 38 good-adherent patients (54%) and 32 poor-adherent patients (46%) in Lifou. This means that 46% of these patients with a previous history of ARF or RHD and receiving BPG injections were at high risk of recurrence of ARF.
The mean and median rate of adherence we found (77% and 82.2% respectively) was lower than the one observed in India par Kumar et al. (mean adherence >90%), but was higher than those assessed in Australia by Stewart et al. (median rate of injections 54%), by Eissa et al. in a remote Top End Aboriginal community (58% of patients received <80% of doses), by Mincham et al. in the Kimberley region in Western Australia (median adherence = 67%) and by Seckeler et al. in Northern Mariana Islands (median adherence = 69.2%) [16, 18, 19, 21, 25]. A study conducted in Egypt showed that 64.6% of patients had an adherence ≥84%, nevertheless the study samples can hardly be compared (20% of children under oral antibioprophylaxis, injections of BPG delivered every 2 weeks) . Ehmke et al.'s study in Iowa, where the overall adherence was 64.6%, presents the same objections to comparison: paediatric population, oral antibioprophylaxis .
The wide range of indicators used in these different studies makes comparison particularly difficult and highlights the necessity of standardized indicators to evaluate adherence.
In our study, the multivariate analysis could determine three independent factors protectors of poor adherence: a demographic factor, ≥6 individuals in the household; a health system-related factor, an adequate healthcare coverage; a condition-related factor, a previous history of symptomatic ARF. Two studies, conducted in the USA, tried to determine an association between the number of individuals of the household and the adherence. Gordis et al. in 1969, and Ehmke et al. in 1980 found that a large number of siblings was a risk factor of poor adherence [26, 27]. In our study, we postulate that a large number of siblings in the household could improve the adherence probably because of the presence of a big brother or sister. They could accompany the child to the health center or take care of the household during the time of the consultation. This hypothesis is consistent with Gordis et al. study in which being unaccompanied by parent at clinical visits was associated with poor adherence. Mincham and Harrington, in two qualitative studies conducted in Australia, showed that an active recall system was a major determinant of adherence [28, 29]. This secondary prevention strategy is indeed highly recommended by the WHO and the World Heart Federation [4, 6].
The association between the cost of medication and a poor adherence affects particularly low income populations [15, 30–32]. To our knowledge no study ever analyzed this association in secondary prophylaxis to ARF and RHD, probably because it is usually free of charge in most countries. In Lifou, BPG injections are free but the copayment required for cardiologist reviews and transports to the cardiologist might have led to a negative perception of the health system and a feeling of not “belonging” to the health service. According to Harrington and Mincham, those representations of health system were responsible of poor adherence among Aboriginal patients [28, 29]. An adequate healthcare coverage might be the consequence of a good adherence. Indeed, good adherent patients having frequent interactions with health staff could have a better track of their administrative and medical record.
Patients with a previous history of symptomatic ARF had a better adherence than patients who were diagnosed with RHD without history of ARF. It is described that among chronic diseases, asymptomatic diseases (diabetes, hypertension, osteoporosis…) are more likely to generate poor adherence . Patient’s perception of the disease gets modified by the existence of symptoms and the level of disability. Gordis et al. determined that having ARF with “no restriction of activity” was a risk factor of poor adherence among children . Fear of recurrence of intense and painful symptoms might enhance adherence, unlike those diagnosed with RHD without history of ARF. Health education and sensitization in order to modify risks perception shall therefore be promoted.
Our retrospective cohort study of patients receiving antibiotic prophylaxis for ARF recurrence in Lifou was quite exhaustive; three patients only could not be contacted. A single investigator (BG) interviewed patients and collected data, therefore limiting the risk of variability. The study was led on a small island where all the health structures could be visited, which facilitated the data collection. By screening data, this study allowed us to register three new patients in the local register, to realize numerous demands for full medical coverage, to update medical and personal data and to provide information to cease two patients’ antibiotic prophylaxis. Nevertheless, one of the limitations of this study, beside its retrospective design, was the sample size, resulting in a lack of statistical power. Another limitation was that we were not able to perform a sub-group analysis comparing children aged less than16 years and adults because of the small sample size giving a lack of power.