Calculating a Control Mean and Range

1. Collect a minimum of twenty data points for each level of control.
   • Obtain data points from twenty separate analytical runs reflecting variables such as calibration frequency, change of reagent or reagent lot, operator technique, temperature and humidity of testing location, daily and weekly maintenance, and so on.

     *Based on the Clinical and Laboratory Standard Institute (CLSI) recommendation for the minimum number of data points necessary to calculate a range.

   • Compare new control products to previously validated controls (parallel testing).
2. Calculate the mean and standard deviation from the data points collected.
   • Use a statistical test for outliers before eliminating any questionable data points.
   • Calculate the statistical control limit from the mean ±2SD and the mean ±3SD.

Important: Use product insert ranges as guidelines only. Ranges are based on reagent lots and materials available at the time of value assignment. During the life of the control lot, manufacturers may reformulate tests or begin using a new source of raw materials for kit/reagent production. Published ranges cannot account for variables such as instrumentation software updates or performance differences over time.