Quality assurance/assessment is a continual process and demonstration of the quality of individual laboratories in the GMRLN is critical to maintain confidence by stakeholders and colleagues in the surveillance programme that the laboratories are providing results with high sensitivity and specificity. The WHO measles and rubella EQA programme is a coordinated global activity to provide annual proficiency panels, evaluate results, and distribute reports.
Although the annual panels provide only a snapshot for quality assessment, the results provide an assessment tool that has proven to be valuable for individual laboratories and for aggregate evaluation of the laboratory network performance. In addition, the assays and methods that may vary across laboratories can be compared through the distribution and testing of a global proficiency panel.
The proficiency panels for IgM and molecular detection for both measles and rubella require a massive effort to produce and distribute. The details of the proficiency programmes for measles and rubella IgM and for molecular testing available for laboratories in GMRLN laboratories are provided below.
Measles and rubella IgM proficiency panel
An annual proficiency programme for measles and rubella IgM has been conducted since 2001 for laboratories within the WHO laboratory network [4]. The RRL in Australia, (Victorian Infectious Diseases Reference Laboratory, VIDRL), assembles the panels using serum that has been provided by network laboratories. The annual panels are identical, consisting of 20 serum samples that have been thoroughly evaluated prior to inclusion in the panel. All samples are tested for both measles and rubella IgM. More than 250 laboratories in GMRLN participate in the annual programme. Laboratories are required to test the panels as they would routine samples and report detailed results of the samples as well as assay validation data within the prescribed timelines.
With the global distribution of the proficiency panel, problems with IgM assays used for measles and rubella surveillance in the GMRLN laboratories can be detected. The performance of each laboratory is assessed according to concordance of expected results, completeness of data provided, and timeliness of the results returned to VIDRL.
Points are deducted if incorrect sample results are reported, which may be due to an error in interpretation or in the transcription of results. In addition, deductions to the final score will occur if kit or assay information, validation data, and details of any in-house control sample used are not provided or not complete. A score of <90% is considered a red flag and may have a negative impact on the laboratory’s accreditation status. Scores below 80% require urgent action to resolve any deficiencies in the laboratory or in the performance of their assays.
Measles and rubella proficiency panel for molecular testing
Molecular characterization of measles and rubella viruses is an important component of surveillance and a valuable tool for measuring the effectiveness of measles and rubella control and elimination programmes. Many laboratories in the global network now have the capacity to perform nucleic acid amplification with samples collected from measles and rubella cases, however some laboratories may not have the capacity to perform sequencing.
The WHO programme for molecular external quality assurance (mEQA) for the measles and rubella laboratories in GMRLN was initiated in 2014 by the Global Specialized Laboratory at CDC, Atlanta, USA. The mEQA panels consist of samples for both measles and rubella virus prepared from lysates of infected cells that had been dried onto FTA® Cards. Six mm disks are cut from the FTA cards and shipped to participating laboratories. The disks are stable for shipping at ambient temperature when packaged with a desiccant. The components of the panels have been coordinated between RRLs and INSTAND e.V., a reference testing institute in Berlin. RNA extracted from the disks can be used for RT-qPCR/RT-PCR and genotype identification. In order to achieve the maximum points, the report should demonstrate:
• Correct identification of measles or rubella RNA from all positive samples
• No false positive results from the negative samples
• Adequate positive and negative controls on PCR reactions
• Correct identification of the measles or rubella genotypes from each positive sample
• Ability to amplify and sequence the complete WHO standard sequencing windows for measles (N-450) and rubella (739nt)
All network laboratories performing molecular techniques for measles and rubella surveillance must achieve a passing score in the annual mEQA so that molecular results reported to the surveillance programme can be accepted. Evidence of performance issues in individual laboratories will require development of an action plan to address these issues and successful completion of a subsequent mEQA panel before routine molecular testing can proceed.
Laboratories that do not have the capacity for determining genotypes from measles and rubella cases or have not passed the mEQA should send suitable samples from representative outbreaks to the designated reference laboratory, in consultation with the regional lab coordinator.