Lab Testing for Measles at the MDH Public Health Laboratory
Though measles is no longer endemic in the United States, outbreaks continue to occur as a result of internationally imported or import-linked cases. Continued success in disease reduction is dependent on maintaining awareness of the disease along with improving vaccination rates.
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Clinical features and differential diagnoses
Report suspect case
Lab tests offered at MDH-PHL
Preferred specimens: PCR
Specimen collection: PCR
Approved swabs and media
Transporting specimens to MDH
Measles and rubella should both be included in the differential diagnosis of patients presenting with an acute generalized rash and fever.
Measles is characterized by:
- A generalized maculopapular rash lasting
3 days or more
- Fever of 101°F (38.3°C) or higher
- Cough, coryza, or conjunctivitis
Rubella is characterized by:
- Acute onset of a maculopapular rash lasting
less than 3 days
- Fever higher than 99°F (37.2°C)
- Arthralgia, arthritis, lymphadenopathy, or conjunctivitis
MDH also encourages health care providers to consider other infectious and non-infectious etiologies that may cause generalized rash, including:
- Coxsackievirus, Echovirus, Epstein-Barr virus, Erythema infectiosum (Fifth Disease), HIV, Kawasaki disease, Roseola infantum, Scarlet fever, Pharyngoconjunctival fever
- Dengue fever, Rocky Mountain spotted fever
- Dermatologic manifestations of Viral hemorrhagic fevers (VHFs)
- Cutaneous manifestations of syphillis
- Toxic Shock Syndrome
- Drug reactions (e.g. antibiotics)
- Contact dermatitis
Suspect cases of measles (rubeola) must be reported to the Minnesota Department of Health (MDH) immediately.
All suspect cases of measles and specimens submitted for testing must be coordinated with an MDH epidemiologist at 651-201-5414 or toll-free at 1-877-676-5414. Failure to contact MDH prior to submitting a specimen to the Minnesota Department of Health’s Public Health Laboratory (MDH-PHL) will result in a delay in testing.
Measles Real-Time Polymerase Chain Reaction (RT-PCR, or PCR) is available for measles case confirmation at MDH-PHL. Providers are encouraged to collect and send a PCR specimen to MDH-PHL when measles is suspected. Contact an MDH measles epidemiologist (see Report suspect case) to coordinate specimen submission.
Serologic testing (measles-specific IgM or acute/convalescent IgG) can still be used in conjunction with clinical and epidemiologic data to confirm measles; however, due to concerns with falsely positive/negative results, serologic testing for diagnostic purposes will be discontinued at MDH-PHL.
Serum specimens for serologic testing may be sent to your facility’s usual reference laboratory, and a specimen for PCR should be sent to MDH-PHL.
A clinical specimen for PCR should be taken as soon as measles is suspected. Viral RNA is more likely to be detected when the specimen is collected as soon as possible after rash onset. Ideally, a specimen for measles PCR should be obtained within 0-3 days of rash onset (0-9 days at most). Consider the rash onset date as day ‘0.’ Viral isolation requires the same specimens and may be done if PCR is negative.
Please send one (1) of the following specimens to the MDH-PHL, in order of preference:
- Throat swab
- Nasal, nasopharyngeal swab, or nasal wash
- Urine specimenǂ
ǂIf date of specimen collection is on day 5-9 after rash onset (day 0), urine is preferred over other specimens. If date of specimen collection is already more than 9 days past rash onset, PCR is less likely to detect viral presence and may give false negative results.
In accordance with recommendations from the Centers for Disease Control and Prevention, the MDH lab routinely tests for both measles and rubella when specimens are submitted for either disease.
Throat swab: Vigorously swab tonsillar areas and posterior nasopharynx with a viral culturette. Use tongue blade to depress tongue to prevent contamination of swab with saliva. Place swab into viral transport medium (VTM) (see Approved swabs and media).
Nasal or nasopharyngeal swab: Use sterile swabs to swab the nasal passage or the nasopharynx with either a viral culture swab or culturette. Place swab into VTM.
Nasal wash (two techniques):
Use a syringe attached to a small plastic tube and 2 ml of VTM. After placing VTM in the nostril, aspirate as much of the material as possible and rinse the tube with the original (2 ml) of VTM.
- Or -
Use sterile swabs to swab the nasopharynx and throat with either a viral culture swab or culturette. Place both swabs in a tube containing 2-3 ml of transport medium. The virus is extremely cell-associated, so attempt to swab the throat and nasal passages to collect epithelial cells. After swabbing, place the swab back in the transport sheath.
Urine specimen: Collect 10-40 ml of urine in a STERILE 50 ml centrifuge tube or a urine specimen container. First-morning voided specimens are ideal, but any urine collection is adequate. Have patient void directly into container, collecting from the first part of the urine stream if possible.
- Balanced salt solutions (BSS)
- Sterile isotonic solutions
- Phosphate buffered salines (PBS)
- Stuart’s Liquid Media
- BBL Culture Swab
- Wood-tipped applicators
- Calcium-alginate tipped swabs
- Charcoal swabs
- Gel swabs
- Anaerobic media
NOTE: Flocked swabs are preferred for specimen collection. VTM containing ~1% protein (e.g., bovine serum albumin or gelatin) best supports measles virus; however, sterile saline is acceptable.
- Label all tubes/containers with the following information:
- Patient name
- Patient date of birth
- Date specimen collected
- Specimen type
- Include an Infectious Disease Testing and Submission Form for each specimen. Please fill out the form as completely as possible and be sure to indicate which test is requested.
- Specimens should be kept and transported at refrigeration temperature (2-8° C).
- Before shipping, always consult with an MDH epidemiologist at 651-201-5414 or toll-free at 877-676-5414.
- Send to MDH Public Health Laboratory via overnight shipping.
- For help with packaging and shipping, call MDH-PHL Biological Accessioning at 651-201-4953.
Send specimens to arrive Monday-Friday before 4:30 p.m. to:
MDH Public Health Laboratory
Attn: Biological Accessioning
601 Robert St. N.
St. Paul, MN 55155-2531