42 CFR §493.1236

1. (a)The laboratory must review and evaluate the results obtained on proficiency testing performed as specified in subpart H of this part.
2. (b)The laboratory must verify the accuracy of the following:
   1. (1)Any analyte or subspecialty without analytes listed in subpart I of this part that is not evaluated or scored by a CMS-approved proficiency testing program.
   2. (2)Any analyte, specialty or subspecialty assigned a proficiency testing score that does not reflect laboratory test performance (that is, when the proficiency testing program does not obtain the agreement required for scoring as specified in subpart I of this part, or the laboratory receives a zero score for nonparticipation, or late return of results).
3. (c)At least twice annually, the laboratory must verify the accuracy of the following:
   1. (1)Any test or procedure it performs that is not included in subpart I of this part.
   2. (2)Any test or procedure listed in subpart I of this part for which compatible proficiency testing samples are not offered by a CMS-approved proficiency testing program.
4. (d)All proficiency testing evaluation and verification activities must be documented.