Examining patterns in opioid prescribing for non-cancer-related pain in Wales: preliminary data from a retrospective cross-sectional study using large datasets.

This is the first large-scale, observational study of opioid prescribing in Wales.Over 1 million individual, anonymised medical records have been searched in order to develop the study cohort, thus reducing recall bias.Diagnosis and intervention coding in the Primary Care General Practice database is limited at input and may lead to under-reporting of diagnoses.There are limitations to the data available through the Secure Anonymised Information Linkage databank because anonymously linked dispensing data (what people collect from the pharmacy) are not currently available. Consequently, the results presented here could be seen as an 'intention to treat' and may under- or overestimate what people in Wales actually consume.