Exhibiting caution with use of big data: The case of amphetamine in Iceland's prescription registry.

BACKGROUND: Data from large electronic databases are increasingly used in epidemiological research, but golden standards for database validation remain elusive. The Prescription Registry (IPR) and the National Health Service (NHS) databases in Iceland have not undergone formal validation, and gross errors have repeatedly been found in Icelandic statistics on pharmaceuticals. In 2015, new amphetamine tablets entered the Icelandic market, but were withdrawn half a year later due to being substandard. Return of unused stocks provided knowledge of the exact number of tablets used and hence a case where quality of the data could be assessed. OBJECTIVE: A case study of the quality of statistics in a national database on pharmaceuticals. METHODS: Data on the sales of the substandard amphetamine were obtained from the Prescription Registry and the pharmaceuticals statistics database. Upon the revelation of discrepancies, explanations were sought from the respective institutions, the producer, and dose dispensing companies. RESULTS: The substandard amphetamine was available from 1.9.2015 until 15.3.2016. According to NHS, 73990 tablets were sold to consumers in that period, whereas IPR initially stated 82860 tablets to have been sold, correcting to 74796 upon being notified about errors. The producer stated 72811 tablets to have been sold, and agreed with the dose dispensing companies on sales to those. The producer's numbers were confirmed by the Medicines Agency. CONCLUSION: Over-registration in the IPR was 13.8% before correction, 2.7% after correction, and 1.6% in the NHS. This case provided a unique opportunity for external validation of sales data for pharmaceuticals in Iceland, revealing enormous quality problems. The case has implications regarding database integrity beyond Iceland.

Use of SE-30 as a stationary phase for the gas-liquid chromatography of drugs.

The dimethyl silicone elastomer SE-30 has been chosen as the preferred liquid phase for the gas-liquid chromatographic analysis of drugs, and retention index data have been compiled for 480 drugs and commonly occurring chemicals such as plasticisers. The inter-laboratory variation in measurement of retention indices has been measured for three drugs in eleven laboratories and the standard deviations were between 20 and 15 retention index units.