Sampling method proficiency or efficacy can be described as the overall sampling “probability of success” and is highly dependent on each of the three steps or segments of the sampling process: Location/Discovery; Extraction, and Elution. Since each step typically occurs in the same sequence, each prior step highly influences all subsequent steps. Additionally, a low probability coefficient for any of the three general steps significantly lowers the final probability that a true representative sample of the surface in question will be provided to the detection process.
For example, in the overall sampling process, if the probability of accurately locating an actual “hot spot” is low due to the limited sampling area allowed per sample, the success of the whole sampling process is in serious jeopardy. Obviously, if the first step is not successful, subsequent steps are meaningless. However, if the location step is successful but low, and if the second step of extraction of the pathogens from the surface is correspondingly low, perhaps due to harbored pathogens located below the immediate surface for example, the combined effects of these first two segments/steps of the sampling process are further reduced or biased downward. Consequently, the third step of elution or recovery of the contaminate from the sampling device inherits a predetermined lower probability of success because there are simply lower total numbers of bacteria present in that sample coming up for further lab processing.
The Sampling Proficiency (SP) can be calculated experimentally by determining the product of the combined probabilities (coefficients) of success of each of the three main sampling steps. That is, Location/Discovery (LD) x Extraction (Ex) x Elution (El) = Sampling Proficiency (SP). The final value of the SP reflects the true probability of an accurate analysis of the surface of interest. It is apparent that a higher SP values represent a greater efficacy of the overall sampling method or device.