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Designing a collaborative study.
T. C. NELSEN (1). (1) independent, Port Byron, IL, U.S.A.
The purpose of a collaborative study is to provide estimates of the performance characteristics for an analytical method when that method is used in actual practice. A collaborative study will provide estimates of expected variance within laboratories (r =repeatability) and between laboratories (R =reproducibility). Guidelines suggest a minimum of 8 laboratories analyzing at least 7 different materials of which at least 5 are different materials and 2 are blind replicates. These International guidelines were established in 1987 to define performance characteristics and provide procedures for calculating those characteristics. These guidelines are a “living” document and are continually updated and expanded. More recent publications describe Standard Method Performance Requirements (SMPRs). Think of a collaborative study in three steps. Step 1 is in your laboratory where you optimize the method, check for selectivity and sensitivity and determine which materials are appropriate for the method. Step 2 is a “mini-collab” in which you send materials to 2 or 3 other labs and then check for ambiguities in the method description or systematic biases in results. Step 3 is the official full collaborative study which you organize with the input of the appropriate technical committee. The international guidelines are written generally for methods to measure constituent concentrations but can be modified for other methods such as physical testing, biological activity or detections. Guidelines are also available for qualitative measures. In all cases, consult a statistician before you start.
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