Workup of a proficiency challenge failure:
(1) Repeat testing on the proficiency samples, if possible. It is important to carefully store the samples for this purpose.
(2) Look at the quality control records at the time of testing.
(3) Review the instrument's performance records.
(4) Review possible problems with the method being used.
(5) Review problems with the reagent lots.
(6) Look for possible problems in the proficiency material.
(7) Consider problems in reconstituting, diluting or mixing the proficiency material.
(8) Evaluate the technologist who performed the testing.
(9) Check for clerical errors in recording or entering results.
(10) Look for errors in concentration units used to report the results.
(11) Look at results reported by other testing sites.
(12) Consider errors at the regulatory agency.
Possible problems with proficiency material:
(1) Degradation after exposure to temperature extremes if shipped during winter or summer.
(2) Matrix effect.
(3) Bacterial or fungal overgrowth.
Clerical errors may include:
(1) A transcription error.
(2) Wrong bubble filled.
(3) Wrong method indicated.
(4) Wrong instrument indicated.
Sometimes no reason for the failure can be found after a careful review. However, this conclusion should only be reached after a very careful evaluation.
Clerical errors, proficiency material and mixing problems are probably the most common failures in a well-run laboratory.
