Annex 1Laboratory procedures

Publication Details

For further details, see the measles laboratory manual5

Collection and shipment of single blood specimens for IgM serology

Blood specimens should be collected at the first contact the person has with the healthcare provider, but within 28 days of rash onset. Collection procedure is as follows:

  • Collect 5 ml blood by venepuncture into a duly-labeled sterile tube.
  • Whole blood should be centrifuged at 1000xg for 10 minutes to separate the serum.
  • Blood can be stored at 4–8 °C for up to 24 hours before the serum is separated.
  • Do not freeze whole blood.
  • If there is no centrifuge, blood should be kept at room temperature (4–30 °C) until there is complete retraction of the clot from the serum.
  • Carefully remove the serum, avoiding extracting red cells, and transfer aseptically to a sterile labeled vial.
  • Store serum at 4–8 °C until it is ready for shipment. The serum can be stored in refrigeration for a maximum period of seven days. Serum must be frozen at −20 °C if it is going to be stored for longer periods.

A second specimen may occasionally be required if the first specimen had an equivocal result, or if the clinician needs to consolidate the diagnosis on an individual patient who gave an initial negative result. The second specimen may be collected at any time between 3–28 days after rash onset, preferably at least 10 days after the first specimen.

Virus isolation should be performed to identify the measles genotype causing the outbreak. Urine or nasopharyngeal samples need to be collected from 5–10 cases and sent to specialized reference laboratories — for more details see the AFRO Guidelines for Measles Surveillance (25).

Storage of specimens outside the laboratory

Whole blood may be held at refrigerator temperature (4–8 °C) if it can be transported to arrive at the testing laboratory within 24 hours. If this is not possible, the tube must be centrifuged to separate the serum, which is transferred to a sterile, labeled screw-capped tube for transport to the laboratory. Sterile serum must be shipped on wet ice within 48 hours, or stored at 4–8 °C for a maximum period of seven days.

For longer periods, sera must be frozen at −20 °C and transported to the laboratory on frozen icepacks. Repeated freezing and thawing can have detrimental effects on the stability of IgM antibodies.

Shipment of specimens

Specimens should be shipped without delay, and should be accompanied by a specimen form indicating date of collection and type of specimen, date sent to the laboratory, date of arrival, and date of results. A laboratory request form should also be completed at the time of specimen collection and should accompany all shipments. The latter form should include the following data: patient identification (unique ID, name, place of residence, age); basic clinical information (date of onset of rash, whether patient fulfils case definition), and immunization history (number of doses of measles-containing vaccine, date of last dose). Shipment procedures are as follows:

  • place specimens in zip lock or plastic bags;
  • use Styrofoam boxes or a thermos flask;
  • place specimen form in plastic bag and tape to inner top of Styrofoam box;
  • if using ice packs (these should be frozen), place ice packs at the bottom of the box and along the sides, place samples in the centre, then place more ice packs on top;
  • arrange shipping date;
  • when arrangements are finalized, inform receiver of time and manner of transport.