Immunosorbent assay- detect the virus specific IgM or IgG antibodies.
Greater than fourfold rise in titer between acute and convalescent sera and cerebo spinal
fluid containing virus specific IgG or IgM or both are the diagnostic features.
Real-time polymerase chain reaction (RT-PCR)- is valuable in the early confirmation of
arbovirus infections, particularly chikungunya. However, the value of RT-PCR is limited to
diagnosis in the viraemic phase, with later infection requiring serology.
Direct immunofluorescence assay -to detect chikungunya IgM has a high sensitivity and
specificity and is used in the latter. stages.However, the use of these tests in the tropics may be limited to the financial strains.
A complement fixation test: Which provides antigen to antibody reactions.
Viral culture: A blood or fluid is withdrawn and the investigations are made.
Laboratory criteria for measles diagnosis are:
- a positive serologic test for measles IgM antibody, or
- a significant rise in measles antibody level by any standard serologic assay, or
- isolation of measles virus from a clinical specimen.
A laboratory-confirmed case need not meet the clinical case definition. Serologic confirmation should be attempted for every suspected case of measles and is particularly important for any case that cannot be epidemiologically linked through a chain of transmission to a confirmed case. However, reporting of suspected or probable cases, investigation of cases, and the implementation of control activities should not be delayed pending laboratory results.
Blood for serologic testing should be collected during the first clinical encounter with a person who has suspected or probable measles. The serum should be tested for measles IgM antibody as soon as possible using an assay that is both sensitive and specific (e.g., direct-capture IgM EIA method). Correct interpretation of serologic data depends on the timing of specimen collection in relation to rash onset and on the characteristics of the antibody assay used. This timing is especially important for interpreting negative results because IgM antibody may not be detectable with some less sensitive assays until at least 72 hours after rash onset. Measles IgM may be detectable at the time of rash onset, peaks approximately 10 days after rash onset, and is usually undetectable 30-60 days after rash onset. In general, if measles IgM is not detected in a serum specimen obtained in the first 72 hours after rash onset from a person whose illness meets the clinical case definition for measles, another specimen should be obtained at least 72 hours after rash onset and tested for measles IgM antibody. Measles IgM is detectable for at least 1 month after rash onset.