Understand PT Scoring Rules
PT provides three shipments (testing events) per year. Each shipment contains five samples for each test (analyte) performed, except for microbiology where a combination of 5 tests per shipment is allowed. To pass a PT event, a laboratory needs a score of at least 80% (4 out of 5 correct responses) for each analyte. Labs must also attain a minimum of 80% for each specialty (chemistry, hematology, etc.) as well as a total event score of at least 80%. Some critically significant tests such as blood grouping and typing require a 100% score to pass.
Overall PT performance is determined by the “two out of three” rule. A laboratory that fails two consecutive or two of three testing events is “unsuccessful” and subject to sanctions. Technically, sanctions for unsuccessful PT include voluntary withdrawal of a laboratory’s CLIA certificate for the specialty, subspecialty or test. This prohibits testing some or all of the failed analytes by any method. By passing two subsequent consecutive PT events, a lab may have its certificate reinstated, and may resume testing.
If the two out of three rule is broken, most likely a HCFA/COLA inspector will contact you to ensure that the cause for failure was determined and that remedial action was taken. If not, you may be required to submit a plan of correction and be subsequently monitored by additional PT or an on-site inspection to evaluate progress.
Enroll For The Correct Tests
CLIA mandates that laboratories subscribe for every "regulated" non-waived test performed where a PT program is available. A list of regulated analytes is in the February 28th, 1992 Federal Register.
Follow PT Directions to the “T”
Most PT failures are due to factors other than analytical problems with a test or an instrument. These controllable conditions include incorrect dilutions or clerical mistakes such as transposing numbers onto the answer block, not completely filling out the report form, or not returning results before the due date.
Testing Proficiency Samples
Handle PT specimens exactly like patient specimens to the extent possible, i.e., test the same amount of times as patient specimens using the same instrument or kit used for patient specimens. Repeat a PT test only if a patient sample with that value would have been repeated. Never send PT samples to a commercial laboratory! Document all steps in the proficiency testing process including the date samples were received, date tested, lot numbers of reagents used, and the person who performed the test. This information will be invaluable when investigating the cause of a PT failure.
Investigating PT Failures
Investigate PT failures as soon as an unsatisfactory score is received. Gather all PT records and try to determine the probable cause. Some serum-based PT samples can be stored frozen and retested if failure occurs. Even if the cause of PT failure can’t be pinpointed, document all investigative actions on the Proficiency Testing Failure Review Log. Take corrective action before the next PT event to avoid breaking the two out of three rule. Examples of corrective action are calibrating at more frequent intervals, reducing the acceptable control range, or retraining an employee.
Retaining PT Records
Save all PT records for at least two years.