Barry Gribben

National prevalence of gout derived from administrative health data in Aotearoa New Zealand

OBJECTIVE Previous small studies in Aotearoa New Zealand have indicated a high prevalence of gout. This study sought to determine the prevalence of gout in the entire Aotearoa New Zealand population using national-level health data sets. METHODS We used hospitalization and drug dispensing claims for allopurinol and colchicine for the entire Aotearoa New Zealand population from the Aotearoa New Zealand Health Tracker (ANZHT) to estimate the prevalence of gout in 2009, stratified by age, gender, ethnicity and socio-economic status (n = 4 295 296). RESULTS were compared with those obtained from an independent large primary care data set (HealthStat, n = 555 313). Results. The all-ages crude prevalence of diagnosed gout in the ANZHT population was 2.69%. A similar prevalence of 2.89% was observed in the HealthStat population standardized to the ANZHT population for age, gender, ethnicity and deprivation. Analysis of the ANZHT population showed that gout was more common in Māori and Pacific people [relative risk (RR) 3.11 and 3.59, respectively], in males (RR 3.58), in those living in the most socio-economically deprived areas (RR 1.41) and in those aged >65 years (RR >40) (P-value for all <0.0001). The prevalence of gout in elderly Māori and Pacific men was particularly high at >25%. CONCLUSION Applying algorithms to national administrative data sets provides a readily available method for estimating the prevalence of a chronic condition such as gout, where diagnosis and drug treatment are relatively specific for this disease. We have demonstrated high gout prevalence in the entire Aotearoa New Zealand population, particularly among Māori and Pacific people.

How much variation in clinical activity is there between general practitioners? A multi-level analysis of decision-making in primary care.

Objectives: There is considerable policy interest in medical practice variation (MPV). Although the extent of MPV has been quantified for secondary care, this has not been investigated adequately in general practice. Technical obstacles to such analyses have been presented by the reliance on ecological small area variation (SAV) data, the binary nature of many clinical outcomes in primary care and by diagnostic variability. The study seeks to quantify the extent of variation in clinical activity between general practitioners by addressing these problems. Methods: A survey of nearly 10 000 encounters drawn from a representative sample of general practitioners in the Waikato region of New Zealand was carried out in the period 1991-1992. Participating doctors recorded all details of clinical activity for a sample of encounters. Measures used in this analysis are the issuing of a prescription, the ordering of a laboratory test or radiology examination, and the recommendation of a future follow-up office visit at a specified date. An innovative statistical technique is adopted to assess the allocation of variance for binary outcomes within a multi-level analysis of decision-making. Results: As expected, there was considerable variability between doctors in levels of prescribing, ordering of investigations and requests for follow up. These differences persisted after controlling for case-mix and patient and practitioner attributes. However, analysis of the components of variance suggested that less than 10% of remaining variability occurred at the practitioner level for any of the measures of clinical activity. Further analysis of a single diagnostic group - upper respiratory tract infection - marginally increased the practitioner contribution. Conclusions: The amount of variability in clinical activity that can definitively be linked to the practitioner in primary care is similar to that recorded in studies of the secondary sector. With primary care doctors increasingly being grouped into larger professional organisations, we can expect application of multi-level techniques to the analysis of clinical activity in primary care at different levels of organisational complexity.

Rational Prescribing and Interpractitioner Variation: A Multilevel Approach

There are marked geographical variations in rates of medical and surgical intervention at every level of aggregation and in every aspect of medical practice. These data raise a range of important theoretical, methodological, and policy issues. Much the same pattern of variation characterizes the prescription and consumption of therapeutic drugs. Data from a survey of general practice in New Zealand confirm the existence of extensive variability in prescribing. Multilevel techniques are deployed to isolate the specific interpractitioner element in this variability. Controlling for patient, diagnostic, and practitioner variables improves the predictive power of the model but does not reduce the extent of interpractitioner variability in prescribing rates. The existence of such variability raises questions about the role of clinical uncertainty and professional autonomy in the promotion of rational therapeutics in medical practice.

Do physician practice styles persist over time? Continuities in patterns of clinical decision-making among general practitioners.

Objectives: This study seeks to determine whether there are identifiable differences in patterns of clinical decision-making among family physicians, and whether these patterns persist over time. Methods: A representative cross-sectional survey of general practice encounters in the Waikato region of New Zealand in 1979–1980 was repeated in 1991–1992. Patterns of clinical decision-making were operationalised as practitioner rates for writing a prescription, ordering a laboratory test or radiological examination and the recommendation of a future follow-up office visit at a specified date. Comparable data were available for a cohort of 50 physicians in both surveys. Multi-level techniques and a simulation exercise were used to study the patterns of decision-making over time. Results: Raw, unadjusted correlations for the 50 family physicians between the two surveys were 0.24, 0.14 and 0.55 for rates of prescribing, investigations and follow-up, respectively. However, these correlations increased substantially, to 0.55, 0.41 and 0.70, once account was taken of case mix, data clustering and inter-practitioner variation in patient sample size. The extent of this recovery of the underlying correlations was confirmed in a parallel simulation exercise. Conclusions: This study confirms the existence of substantial and durable individual practice styles in primary medical care, with implications for the development and successful implementation of clinical guidelines.

DNA‐damaging activity in ethanol‐soluble fractions of feces from New Zealand groups at varying risks of colorectal cancer

Using repair-proficient and repair-deficient strains of E. coli, we investigated the application of a liquid incubation assay to measure the DNA-damaging activity of ethanol-soluble fecal extracts. This method appears to be suitable for the study of a wide range of sample types. It was used to measure the DNA-modifying activity of ethanol-soluble fecal extracts from a group of European colorectal cancer patients. Data were compared with those from Europeans of similar age and sex distribution who did not have bowel cancer. We also studied groups of Maoris, Samoans, and European Seventh-Day Adventists who followed an ovo-lacto vegetarian diet. There are significant levels of DNA-modifying materials in the feces of many Europeans on a mixed diet, regardless of whether or not they have cancer. The number of positive samples was less in the Polynesian groups, and there were no samples that could be unequivocally scored as positive in the Seventh-Day Adventist groups. We conclude that diet can significantly reduce the level of ethanol-soluble mutagens, at least in New Zealand Europeans. The data may provide an explanation for the reduced incidence of bowel cancer in Seventh-Day Adventist groups.

The impact of the new subsidy regime in general practice in New Zealand.

The first substantial change in the New Zealand health care reforms was the introduction in February 1992 of a new subsidy and charging regime in general practice. The paper reports on a comparison of data collected before and after the changes, drawing on GP-patient encounter information. Overall, seasonally adjusted levels of utilisation were maintained in the stage before the introduction of the new regime, declined 15% immediately following the changeover and stabilised thereafter. All patient groups were affected by the decline. Although the elderly were temporarily exempt from the changes, their consultations fell by 10%. Utilisation among beneficiaries--minor gainers from the changes--dropped by 30%. Children were more affected overall, adults less so. There was also some suggestion of greater falls for the lowest socio-economic groups. Activities under the direct control of the practitioner--prescribing and the ordering of tests--showed either little turbulence or no clear pattern of change. It is concluded that, although primary care subsidies and charges had been reshaped to favour poorer people, six months after the introduction of these changes there had been no corresponding redistribution of medical care consumed. Indeed, there is a suggestion that some of the groups ostensibly the target of increased assistance may have been adversely affected by the overall decline in utilisation.

Key informant representations of Maori and other patient fears of accessing general practitioner care for child asthma in Auckland, New Zealand

Fear is seldom reported in the research literature on barriers to accessing general practitioner (GP) care. One reason may be that some patients are unwilling to admit to fear of this care. This is especially so for patients who, for social, cultural and historical reasons, have a poor sense of self, or do not wish to challenge professionals, or both. In New Zealand, the Maori and Pacific peoples are disproportionately characteristic of these patients and have poor access to GP care, including asthma in children. This paper contributes to the literature on using key informants to interpret another group’s needs, and integrates and adds to known patient attitudes that can hinder access to GP services.