the Why of Laboratory Proficiency Testing
(External Quality Assessment – EQA)
presentation is part 1 of a series highlighting
Proficiency Testing as a Laboratory Quality Partner.
When a doctor or patient or family members is told that a laboratory has processed a sample and come to an answer or conclusion, the people involved usually assume that the answer the have been given is correct, and usually they are correct.
Unfortunately that is not always the case. While most errors are of little consequence, sometimes the error can lead to harm to people and public health and can lead to complications and sometimes worse. What studies indicate is that most errors are either not detected or are detected but not reported.
What the world needs is a program that can monitor laboratories, detect errors help them learn and avoid bad outcomes. Fortunately that program exists and is known as Proficiency Testing or External Quality Assessment (EQA)
Proficiency Testing (EQA) is single most important method to ensuring that laboratories are capable to performing tests in a manner that will provide accurate, relevant, understandable information, in a timely manner.
Other techniques such as Quality Control (QC) can ensure that the materials and reagents and equipment that are being used are working as expected, and QC can also ensure that the environment in which the tests are performed is safe and meets requirements, and the staff have the knowledge and understanding necessary to perform the testing.
Measuring test performance is not easily addressed by QC.
Test performance measurement can be done in two ways. Accreditation bodies often perform direct observation which means an auditor watches a person perform a certain test. If they do it consistent with the written procedure, the auditor records the test was done in conformance.
EQA measures differently by looking at the result. If the result is consistent with the expected result, it is deemed as acceptable; if it is not consistent then it can be rated as “essentially consistent” or “not consistent” or “not consistent and dangerous”.
EQA can determine if test performance results in deriving correct results at high frequency every year. Accreditation body observers have few opportunities to watch people performing tests, maybe 2 or 3 once every year or two. EQA monitors laboratories 3 or 4 times a year with a spectrum of tests resulting often in 80 to 100 observations every year.
Both approaches can detect non-conformances or errors (or opportunities for improvement), but the more observations there are the higher the probability of detecting problems.
Studies on laboratory errors indicate erors fall into two main clusters; one group that are "one-offs", the other that are more repetitive. When EQA picks up an error, it may be difficult to say what type has been detected. When one considers that laboratories can do thousands if not millions of tests every year, the EQA-to-Performed Tests ratio is always going to be very small. But when a laboratory has even just a few errors, the statistics of probability strongly suggest that this is a laboratory having repetitive problems.
So if a laboratory can participate in EQA and not have errors detected, that does not mean the laboratory is error-free; it means that the error frequency is sufficiently low and they were not picked up. On the other hand, when EQA does pick up even a few errors what it assuredly means is that the laboratory is making LOTS of mistakes… the vast majority of which are remaining undetected.
So, when the quality focused laboratory is notified of an EQA error, the staff and management are not only obliged to investigate that error to figure out why it happened and put in corrective actions, they ALSO must do a look back and see if they have made a similar errors on patient samples in the past.
Laboratories are busy active places generating lots of important information, but all laboratories can make errors, some of which can cause harm. Programs like External Quality Assessment (or EQA or Proficiency Testing or PT) exist to help laboratories become aware of errors so that they can focus on cause and correction.
Consider your EQA program as one of your QUALITY PARTNERS.