Appendix 4. Laboratory tests


Laboratory confirmation is based on testing for specific antibodies to the measles virus (ELISA detection of IgM antibodies).
Tests based on virus detection (nested RT-PCR) are used not for diagnosing cases but for studying the genome (global measles surveillance) or for isolating the virus.
The specimen collection techniques are the same regardless of test type.

4.1 Specimen collection

Before taking the sample

– Prepare the equipment: gloves, gown, antiseptic, cotton wool or compresses, indelible marker; plastic safety box, etc.
– Fill out the information form and lab test register (see Appendix 3).
– Wash hands or disinfect them with an alcohol-based solution, and don gloves.

After taking the sample

– Sort/discard waste: needles and lancets in a safety box, contaminated material (tongue depressors, cotton wool, etc.) in a trash bin.
– Verify the identity of the patient (tube, filter paper, request form, register).

4.1.1 Collecting capillary blood on filter paper

Equipment
– Filter paper (Whatman 903®: card with four 15-mm diameter circles for receiving the specimen)
– Plastic 10 x 10-cm zip lock bag (bag for medications)
– Sterile lancet
– Silica gel packet

Technique
– Label the filter paper card with the patient’s last name, first name and age, and the location and date of specimen collection.
– Disinfect the finger, allow it to air dry, and prick with the lancet.
– Wipe away the first drop of blood with a compress or cotton wool.
– Collect the blood on the filter paper. Completely saturate the circles on the card. Check to make sure that the paper is saturated on both sides.
– Let the filter paper air dry, away from sunlight and dust, for 2 hours.
– Once it is dry, place the filter paper in the plastic bag, add the silica gel packet, and close.

4.1.2 Collecting oral fluid

Equipment
– Tongue depressor
– Oral specimen collection device (ORACOL® or OraSure®): sponge, shaft, and tube with cap
– Scissors (depending on the device used)

Technique
– Label the tube with the patient’s last name, first name and age, and the location and date of specimen collection.
– Gently rub the sponge, attached to the shaft, along the gum-tooth junction for about 1 minute. The sponge absorbs about 0.5 ml of crevicular fluid.
– Place the whole device (sponge + shaft) in the tube. Follow the manufacturer’s recommendations.
– Close the tube.

4.1.3 Collecting venous blood and preparing serum

Equipment
– Plain (serum) vacuum tube + tube holder (or if not available, a simple plain tube)
– 21G or 23G needle
– Sterile transfer pipette
– Sterile 2-ml cryotube
– UN 3373 isothermal triple packaging container

Technique
– Label the plain tube and the cryotube with the patient’s last name, first name and age, and the location and date of specimen collection.
– Disinfect the puncture site.
– Draw 5 ml of blood in the serum tube.
– If shipping time is less than 24 hours, no preparation is needed; send the whole blood to the laboratory.
– If the shipping time is over 24 hours:
• Centrifuge the blood for 10 minutes at 3000 rpm (1000 g) to obtain serum. If there is no centrifuge, leave the tube in an upright position for one hour at ambient temperature so that the clot retracts, and then refrigerate it until contents are completely separated (serum yellow and clear).
• Draw off the serum with a sterile pipette and transfer it to the sterile cryotube.

4.2 Storing samples 


Storage time

Storage temperature

Comments
Capillary blood≤ 7 daysRoom temp. (< 42 °C)
> 7 days4 to 8 °C

Oral fluid

≤ 7 daysRoom temp. (< 42 °C)
> 7 days

Depends on device1

Use another specimen type, if possible

Whole blood< 24 hours4 to 8 °C
Serum< 7 days4 to 8 °C
> 7 days− 20 °CNo successive freezing/thawing

4.3 Transport, packaging, and shipping

Blood on filter paper and oral swab
These specimens are not considered pathogenic: no triple packaging. However, they must be placed in a waterproof bag (a plastic zip lock bag, for example).

Whole blood or serum
Protect each tube in specific triple packaging that meets the regulations for transporting Category B infectious substances, UN 3733.

Before shipping
Verify that:
– the containers are tightly sealed;
– the information is entered in the laboratory register;
– the patient information form is inside the package.

When shipping
– Write the exact address (including the service and the name of the addressee).
– For whole blood or serum: fill out the information on the outer container (3373).
– Attach all necessary shipping documents.
– Record the shipment to allow follow-up (receipt at lab and transmission of results).
– Alert the services concerned that the sample(s) have been shipped.

4.4 Reference laboratories

Send specimens to national laboratories, if possible; if not, use the closest WHO LabNet laboratory.



Footnotes
Ref Notes
1

The OraSure® device (with transport medium) allows ambient temperature (< 39 °C) transport for up to 21 days.