Participate in a proficiency testing scheme for each examination performed by the laboratory


Internal Quality Control (IQC) must be implemented to have daily control over correct execution of procedures. External Quality Assessment (EQA) is another important tool for controlling quality and provides the laboratory with insight in its performance compared to other laboratories.


EQA can be arranged through participation in programs of proficiency testing (PT), rechecking and retesting, and onsite evaluation by external assessors. See the WHO/CDC/CSLI Laboratory Quality Management System (LQMS) training handbook information sheet in the right-hand column for more information about EQA.

In PT a reference laboratory (organizer of the PT scheme) sends samples with known values for analysis to other laboratories. The values of the samples remain undisclosed to these laboratories while they analyze these samples in the same way as routine examination is done. The results must be reported back to the organizer who will compare the results with the already known value of the samples and determine the correctness of the results produced by the laboratory. Incorrect results point to errors/weaknesses in the system of the participating laboratory which should perform an analysis to identify these errors and correct them.

Ideally, the organizer of the PT scheme must comply with ISO 17043 called "Conformity assessment - General requirements for proficiency testing".

In some geographical areas participation in PT is not always possible or PT may not be available for a certain examination. In this case the laboratory must attempt to set up an "inter-laboratory comparison scheme". In inter-laboratory comparison the laboratory prepares and sends a panel of samples to other laboratories that have to analyze the samples. The laboratory should also analyze the samples itself. The participating laboratories must subsequently report their results back to you (the organizing laboratory). Collect all the results in one overview, perform an analysis of variance and identify significantly deviating results. Make a report including all the results in which the deviating results are highlighted. This report must be send back to all the participating laboratories. If the result produced by you is deviating from results produced by other laboratories, act according to the same procedure as for incorrect/deviating PT results as described above.

The rule is that EQA results will only provide an effective insight into quality performance of the laboratory when the EQA samples are treated in the same way as routine samples. If EQA samples are treated differently from routine samples then the results may be excellent but nothing will be learnt about the quality of the routine services.

Here follows the optimal procedure for dealing with EQA samples:

  • In both PT and inter-laboratory comparison it is crucial that samples are analyzed using the routine methods. The best method is when the laboratory manager codes and secretly adds the EQA samples to the set of routine samples and makes them unrecognizable as EQA samples to staff. The laboratory manager collects the results from the laboratory register after examination. Recording which staff member(s) have analyzed the samples also provides input for staff members' competency assessments.
  • After the samples have been analyzed the laboratory manager must report them before the deadline to the organizer of the EQA scheme in compliance with the guidelines set by the organizer.
  • When the final report from the EQA scheme organizer is received the laboratory manager must see if the results produced by his/her laboratory were correct. The laboratory manager must discuss the results at least with the staff members involved in the examination, but preferably with all the laboratory staff so that everybody knows how the laboratory performs (In that case the name of the person who tested the samples should remain unknown as it is not about persons but about the laboratory performance). If deviating/incorrect results were produced an analysis must be performed to identify the problem and the cause(s) of this problem. When all the causes have been found the laboratory must implement corrective actions to solve the problem and controls must be implemented that indicate when the problem reoccurs. When possible the laboratory should design and implement preventive actions to prevent that the same problems reoccur.
  • In the next EQA round the laboratory must verify that the results are now correct and that the problem does not exist anymore. Note that you can recognize the Plan-Do-Check-Act cycle in this procedure.

It may happen that participation in PT or organization of inter-laboratory comparison is just not possible. In this case, focus on other elements of EQA; set up a rechecking and retesting scheme. In such a scheme different staff members test the same samples and the results are compared, or, even better: another laboratory tests a set of samples and results of the two laboratories are compared.

How & who

Laboratory Manager:

  1. Find a suitable PT scheme for each examination performed by the laboratory and verify if the organizers of the schemes are adhering to the ILAC G13 guideline for the Requirements for the Competence of Providers of Proficiency Testing Schemes. If so, enroll in these schemes.
  2. When EQA samples are received introduce the samples in the routine examination in such way that they are unrecognizable as EQA samples. Follow the Plan-Do-Check-Act procedure described above.
  3. If for a certain examination no PT scheme exist, try to set-up an inter-laboratory comparison scheme with a group of laboratories in the region. In this scheme reports must be drafted that include all the results as reported by all the participating laboratories so that comparison is possible. An analysis of variance must be performed and deviating results must be marked so that the laboratory that produced these results can act with an analysis of the problem and causes and can solve these.
  4. If no PT participation and no organization of an inter-laboratory comparison scheme is possible: set up a rechecking/retesting scheme as described above.

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This activity belongs to the QSE Assessment