Selecting laboratories to test specimens
Access to laboratories with high-quality performance and an acceptable cost per specimen is a critical factor in determining the feasibility of including selected vitamin or mineral biomarkers in a micronutrient survey. The laboratories may be national or international. If international, the survey management team needs to plan for the required export permissions and costs of shipping samples or specimens out of the country, as well as for the requirements for them to be accepted in the receiving country. Identification of laboratories to conduct quality-assured analyses should be done very early in the planning process.
Laboratories under consideration for micronutrient biomarker analysis should first be assessed by experts in the field. The assessment should consider the following criteria:
- The laboratory performs analyses using accepted standard methods (usually the gold standard or an internationally accepted standard);
- The laboratory staff has the technical skills required for performing the analyses;
- The analyses are routinely carried out in the laboratory (within the last few months);
- The laboratory has the ability to analyse the appropriate number of samples daily to provide the necessary throughput for a survey and maintains the instruments in good working condition;
- Quality assurance measures are in place or can be easily set-up including:
- a. Preparing quality control (QC) materials for analysing survey samples
- b. Using bench QC pools for every run
- c. Using blind QC pools for every run
- d. The laboratory participates and performs well in external quality assurance (EQA) programmes, including the Centers for Disease Control and Prevention’s (CDC’s) Vitamin A Laboratory – External Quality Assurance (VITAL-EQA for vitamin A, B vitamins, vitamin D, iron and CRP) programme,1 Ensuring the Quality of Iodine Procedures (EQUIP for iodine) programme,2 the Vitamin D External Quality Assessment Scheme (DEQAS for 25-hydroxy-vitamin D),3 and EQA for the folate microbiological assay (serum and whole blood)
- e. Use of international reference material (where available) to periodically verify the accuracy of other methods used, and acceptable performance for all selected analytes.
It is preferable that a single laboratory analyses all specimens for a specific assay. This will avoid any possible inter-laboratory variation. The ”Questionnaire for laboratory evaluation” online form can assist with the selection process.
Key issues to consider when selecting a method include:
- the type of biological specimens and/or food samples required
- the number and volume of specimens and/or samples to be tested
- the timeline for completing tests (testing large numbers of specimens for certain nutrients may take several months)
- how the specimens should be collected, processed, stored, and transported to the laboratory (this will include any cold chain requirements)
- assay costs
- the requirements and costs of quality assurance processes for each method.