To test for measles, healthcare professionals use several methods involving collection of clinical specimens:

• Swab samples: A nasopharyngeal or throat swab is commonly collected to detect measles virus RNA using real-time RT-PCR. This test is most sensitive when specimens are taken at the first contact with a suspected case, ideally within the first few days of rash onset

• Urine samples: Urine can also be collected for RT-PCR testing, though swabs from the throat or nasopharynx are preferred. Collecting both throat swabs and urine improves detection chances

• Blood samples: Blood is drawn to perform serologic testing. The IgM antibody test detects recent or current measles infection, usually within the first few days after rash appears. If the initial test is negative but suspicion remains, a second blood sample may be collected 3–10 days after symptom onset to detect IgM antibodies. IgG antibody testing can determine immunity from past infection or vaccination

• Additional tests: In some cases, especially if complications like encephalitis are suspected, cerebrospinal fluid may be tested via spinal tap

Summary of specimen types and tests for measles diagnosis:

Specimen Type| Test Type| Purpose| Timing
---|---|---|---
Nasopharyngeal/throat swab| Real-time RT-PCR| Detect measles RNA (active infection)| Within 1–3 days of rash onset (up to 10–14 days possible)
Urine| Real-time RT-PCR| Detect measles RNA| Same as swabs
Blood| IgM antibody test| Detect recent/current infection| Within first few days of rash, repeat if needed
Blood| IgG antibody test| Check immunity| Any time

Testing is usually done promptly when measles is suspected based on symptoms such as rash, fever, cough, runny nose, and conjunctivitis

. Confirmatory diagnosis often combines molecular (PCR) and serologic (IgM) testing for accuracy

. In clinical practice, healthcare providers collect swabs from the throat or nasopharynx and blood samples for serology to confirm measles infection

. These tests help diagnose active infection and support public health efforts to control outbreaks

. Thus, measles testing involves collecting swabs (nose or throat), urine, and blood samples for PCR and antibody tests to confirm infection or immunity.