Recommendations for Setting a Criterion and Assessing Commutability of Sample Materials Used in External Quality Assessment/Proficiency Testing Schemes.

It is important for external quality assessment materials (EQAMs) to be commutable with clinical samples; i.e., they should behave like clinical samples when measured using end-user clinical laboratory in vitro diagnostic medical devices (IVD-MDs). Using commutable EQAMs makes it possible to evaluate metrological traceability and/or equivalence of results between IVD-MDs. The criterion for assessing commutability of an EQAM between 2 IVD-MDs is that its result should be within the prediction interval limits based on the statistical distribution of the clinical sample results from the 2 IVD-MDs being compared. The width of the prediction interval is, among other things, dependent on the analytical performance characteristics of the IVD-MDs. A presupposition for using this criterion is that the differences in nonselectivity between the 2 IVD-MDs being compared are acceptable. An acceptable difference in nonselectivity should be small relative to the analytical performance specifications used in the external quality assessment scheme. The acceptable difference in nonselectivity is used to modify the prediction interval criterion for commutability assessment. The present report provides recommendations on how to establish a criterion for acceptable commutability for EQAMS, establish the difference in nonselectivity that can be accepted between IVD-MDs, and perform a commutability assessment. The report also contains examples for performing a commutability assessment of EQAMs.

A study of the use of free nicotine patches by Indigenous people.

OBJECTIVE: To assess use of free nicotine patches by Indigenous people when offered a brief intervention for smoking cessation, and to assess changes in smoking behaviour at six months. METHODS: We conducted a pre and post study in three Indigenous communities in the Northern Territory. RESULTS: Forty Indigenous smokers self-selected to receive free nicotine patches and a brief intervention for smoking cessation, and 71 chose the brief intervention only. Eighty-four per cent of participants were followed up; 14% of participants could not be located. Fifteen per cent of the nicotine patches group (10% with CO validation) and 1% (CO validated) of the brief intervention only group reported that they had quit at six months. Seventy-six per cent of the nicotine patches group and 51% of the brief intervention only group had reduced their consumption of tobacco. No participant completed a full course of patches. One possible side effect--the experience of bad dreams--was attributed in one community to the person concerned having been 'sung' or cursed. CONCLUSIONS: Free nicotine patches might benefit a small number of Indigenous smokers. Cessation rates for the use of both nicotine patches and brief intervention alone were lower than those in other populations, possibly because the study was conducted in a primary care setting and because of barriers to cessation such as widespread use of tobacco in these communities and the perception of tobacco use as non-problematic.