RAPID DIAGNOSTIC TEST FOR INFLUENZA

RAPID DIAGNOSTIC TEST FOR INFLUENZA

Rapid diagnostic test of influenza identifies the viral nucleoprotein of influenza A and B on the respiratory specimens. The confirmatory test utilizes reverse polymerase chain reaction. polymerase chain reaction uses specific probes for the antigen which hybridizes with specific DNA or RNA of influenza. Rapid diagnostic of influenza does not use molecular assay. The test is less sensitive to detect the presence of the antigen in the respiratory specimen. The test does not require the patients to have the signs and symptoms of influenza but it is used in geographical areas where influenza has been documented, especially during the peak influenza activity in the community.

Before carrying out the test collection of the sample is done. Types of respiratory specimens tested may include the throat swab, nasopharyngeal swab. The swab is taken on the posterior pharynx on the tonsils. The specimen is reviewed to ensure that appropriate specimen is collected. The swab is supplied to the test kit. Some swabs may interfere with the kit and it requires a specialist to conduc

Specimen that requires to be transported should be placed in the appropriate viral transport media. (Papenburg,2017) the second specimen should also be collected for a confirmatory test using viral culture.  The specimen is placed on the kit. The test takes 30 minutes and the results are observed by the colour change or any other visual signal. Rapid diagnostic test serves to be the first line that confirms the presence of the influenza antigen.

The interpretation is as follows the positive results means the antigen as been detected but does not necessarily mean that the viral antigen is viable. The predictive positive results in rapid test is when the highest proportion on the patients have influenza activity. The positive results in the patient who received internasal administration of live attenuated influenza virus vaccine may indicate vaccine virus.

The vaccine contains influenza strain that undergoes replication in the respiratory tissues under lower temperatures other than in the internal temperatures. So, it is possible to detect the presence of the viral strain within 7 days. Thus, false-positive results can occur.

Negative results mean that the rapid influenza test kit did not detect presence on any antigen in the respiratory specimen. It can happen when the influenza activity is low within a certain population. For the children and adults who are hospitalized molecular methods are recommended because it is highly sensitive. The positive results of rapid test do not differentiate between the circulating influenza A among human being and animals.

The purpose of the rapid diagnostic test is to identify the presence of the influenza viral antigen in case of an outbreak especially in institutions, nursing homes, summer camps, schools, hospitals and healthcare’s. In case of any positive results, the authority should be notified immediately and the specimen should be sent to the laboratory for confirmation.

The rapid diagnostic for influenza enables the clinicians to start antiviral treatment in high-risk population. Thus, the formulation of effective control measures and enabling informed decision regarding the test. (Hirayama,2016) The test has shown reduced chest radiography and blood test in care settings and does not prescribe for antibiotic.

Sensitivity of the rapid diagnostic test for influenza is low compared to the molecular method. Thus, the test might produce negative results in some patients with influenza. Specificity of the test also is low and might produce positive results in some patients without the influenza virus. (Stewart,2019) Hence it is commended to use the rapid test and results to be confirmed in the laboratory with the use of polymerase chain reaction. Serological methods that utilize the use of antibodies should not be used as a confirmatory tool in the clinical specimens. Its is because the circulating antibodies IGg does not differentiate between the current and past infections

Factors are affecting the results of the rapid test for testing for influenza the collection of quality respiratory specimen in both the children and adults increase the accuracy and reliability of the test. If the test is to be done in different locations consider choosing appropriate transport media.

Time and illnesses to collect the specimen. The test specimen should be collected 3-4 days of illnesses. (Mott,2017).  This the time when influenza shedding viral is highest and the reliability of the test will be increased. use of special swab increases the reliability and prevent interference with the results.

The rapid diagnostic test does not distinguish between the influenza virus A or B. the test is more sensitive to detect influenza B other than influenza A viral antigen. False-negative results are common where there is a high influenza activity. Molecular technique takes time and gives quality results that recommend for antiviral drugs. Rapid diagnostic test is more quickly and takes about 15-30 minutes and is simple and quick to perform.

Finally, most rapid test utilizes antibodies against the viral nucleoprotein of influenza A or B. an example of rapid test is immunofluorescence assay. Some other rapid test utilizes the digital reader that is higher sensitive for standard interpretation of results.