The primary role of the laboratories in the GMRLN is to provide reliable laboratory testing to support the goals of the national, regional, and global measles and rubella immunization programmes. There are four broad areas of activities that network laboratories carry out in support of these immunization programmes. These are listed and discussed in detail below:
2.3.1 Laboratory testing for case classification and serosurveys
2.3.2 Virologic surveillance for measles and rubella
2.3.3 Communication and documentation of laboratory results and data
2.3.4 Participation in WHO quality assessment and accreditation programmes
2.3.1 Laboratory testing for case classification and serosurveys
The rapid implementation of activities to control transmission is most effective when cases and outbreaks are notified early. Therefore, laboratory testing of clinical samples and results reported for clinically suspected cases must be timely and accurate. The detection of virus-specific IgM is the standard method for case confirmation. However, the use of RT-PCR for direct detection of measles- or rubella-specific RNA is being adopted by many laboratories in the network to complement IgM antibody detection (chapter 6).
The GMRLN is dedicated to full integration of measles and rubella surveillance. A testing strategy or algorithm that is aligned with the epidemiologic situation in the country should be applied to rule out the possibility of either disease. In addition, laboratories are strengthening, or transitioning to, case-based surveillance to support elimination goals and meet laboratory indicators. Additional and specialized testing methods may be required for case classification in elimination settings (chapter 8).
Immunization programmes will need to identify susceptible populations and age groups to target for vaccination campaigns to meet the elimination goals. The laboratories in the GMRLN should be involved at an early stage in planning seroepidemiology studies. Considerations for planning successful seroepidemiology studies and methodologies for measuring population immunity are provided in chapter 9.
2.3.2 Virologic surveillance for measles and rubella
Virologic surveillance is a critical element for measles and rubella immunization programmes and the verification of elimination. The molecular epidemiology of measles has proven useful to support evidence for progress in controlling measles. In near-elimination settings, reduced numbers of lineages within a genotype are typically observed. Additional efforts are needed to fill in gaps in molecular surveillance, particularly for rubella virus [4].
Communication with field immunization staff is important to ensure that adequate samples are collected for genetic characterization. All laboratories that perform genetic analysis to determine genotypes of circulating measles and rubella viruses must report the genotype, relevant sequence data and epidemiological information to WHO measles or rubella sequence databases, MeaNS or RubeNS (chapter 7).
The sub-national and national labs that do not perform molecular testing must promptly notify the appropriate NL or RRL regarding samples that need to be referred for such testing. It is essential that samples are properly processed and stored to preserve the integrity of the samples.
2.3.3 Communication and documentation of laboratory results and data
The format and timing of result reporting at the local, national level, and regional levels will be based on global standards, but operational procedures will be drafted in consultation with appropriate surveillance and immunization programme staff. These operational procedures for conducting surveillance should be clearly assigned and understood. All pertinent information must be transmitted rapidly and reliably from the local units to higher levels of the surveillance or health center offices.
Zero reporting (reporting even if no cases are confirmed) may be required on either a weekly or monthly basis, depending on the recent history of measles or rubella activity. This is an especially important activity in near-elimination and elimination settings.
Regional laboratory coordinators and national laboratories must ensure that the activities completed by the laboratory in support of programme goals are documented. Calculation of the laboratory indicators requires careful management of data. All national laboratories are requested to provide a weekly or monthly report of results to WHO. Laboratories that have been accredited for molecular analysis of measles and rubella viruses should transmit data for wild type virus sequences according to the timeframe specified for genetic data (chapter 7) to the WHO nucleotide surveillance databases MeaNS and RubeNS. For more information on data management and reporting, refer to chapter 11.
2.3.4 Participation in WHO quality assessment and accreditation programmes
Laboratories in the network are required to participate in annual proficiency testing in selected techniques and are evaluated on an annual basis through the WHO accreditation programme. In addition, all laboratories are required to refer samples for confirmatory testing for quality assurance. Usually this is accomplished by forwarding a percentage of samples to a designated network laboratory at the next higher administrative level. Records of samples referred for confirmatory testing, and other necessary elements that demonstrate quality control and quality assurance must be maintained. Chapter 12 covers the requirements for all aspects of quality assurance and quality control, including the WHO-sponsored proficiency programmes and accreditation.