How do I write a lab order for measles and rubella testing?

How to Write a Lab Order for Measles and Rubella Testing

For suspected measles and rubella cases, laboratory confirmation is essential and should include serum testing for measles-specific IgM and rubella-specific IgM antibodies as the primary diagnostic methods. 1, 2

Specimen Collection Requirements

• Order serum measles-specific IgM antibody testing using the direct-capture IgM EIA method, which is the most sensitive and specific test for confirming measles infection 1, 2
• Order serum rubella-specific IgM antibody testing, which is the most commonly used method for serologic confirmation of acute rubella infection 3, 1
• Collect blood specimens as soon as possible after rash onset, ideally within 1-3 days for measles and 1-2 days for rubella 1, 2
• If the first specimen is collected within 72 hours of rash onset and is negative, request a second specimen to be collected at least 72 hours after rash onset for measles and 5 days after rash onset for rubella 3, 1

Additional Testing Options

• For comprehensive diagnosis, consider ordering paired acute and convalescent-phase serum specimens to demonstrate a significant rise in antibody titer 3, 1
  • Acute specimen: Collect within 1-3 days after rash onset
  • Convalescent specimen: Collect 2-4 weeks later for measles and at least 10 days after the acute specimen for rubella
• Include viral isolation testing by requesting collection of:
  • Nasopharyngeal swab/aspirate (for both measles and rubella) 1, 4
  • Urine specimen (particularly useful for measles virus isolation) 1, 4

Critical Information to Include on Lab Order

• Patient's vaccination history (if known) 2, 5
• Date of rash onset (critical for proper test interpretation) 1, 2
• Relevant exposure history to measles or rubella 2
• Clinical symptoms (fever, rash pattern, lymphadenopathy, etc.) 5, 6
• Pregnancy status (if applicable) 6
• Request for RT-PCR testing if available (especially useful for genotyping and epidemiological purposes) 1, 4

Important Considerations

• Specify on the order that results should be reported to local health departments immediately, as both measles and rubella are reportable diseases 3, 2
• Be aware that false-negative IgM results may occur if specimens are collected too early (within first 72 hours of rash onset) 1, 2
• Note that false-positive IgM results can occur with certain viral infections (e.g., parvovirus, infectious mononucleosis, cytomegalovirus) and in patients who are rheumatoid factor positive 3, 2
• For pregnant patients with suspected rubella exposure, clearly indicate this on the lab order as additional testing may be warranted 3, 6