Anti Streptolysin O Rapid Test

Usually, the ASO levels are not detectable for at least a week after an infection, hence ASO tests are not used to diagnose a current acute infection. A throat culture or a rapid strep test is the best method to diagnose strep throat (streptococcal pharyngitis). It is utmost important that the strep throat be promptly identified and treated to avoid complications and passing the infection onto others.

It’s important to realize and strictly follow that no food or drink is to be consumed at least 6 hours before the test. Patients are asked to inform the healthcare provider about any current medications being taken as some medications mainly antibiotics and corticosteroids usually interfere with the test results.

The ASO test results vary with an individual’s age and with respect to individual laborities where tests are conducted however the positive ASO result is when the ASO levels are >200 units/ml. The significance of ASO test is as follows: The ASO level will rise until it reaches its highest level which is considered to be approximately 4 weeks after the throat infection. If the infection is resolved or eliminated, the levels decline. A preliminary low or negative ASO level followed subsequently by low or negative ASO levels usually indicates that no infection has occurred. Initial high or low levels which are followed subsequently by higher levels does indicate a recent or current infection. ASO test is very helpful in a diagnosis of the condition but it does not help in predicting the development of complications after a streptococcal infection. Patients should always remember that the laboratory test results should not be interpreted as results of a stand-alone test and those results have to be interpreted after correlating with suitable clinical findings and supplemental tests/information.

Firstly, all test reagents and samples are brought to room temperature and a disposable pipette is used to draw up and place one free-falling drop of each undiluted sample into its identified circle of the slide. One free-falling drop of positive and negative control is delivered into its identified circle and later the ASO latex reagent is mixed by gently shaking. One free-falling drop of reagent is added to each control and sample. Disposable pipette is discarded and it’s required to slowly rock the slide for exactly 2 minutes and observe for agglutination under a high intensity light. Eventually, the results are recorded and the glass slide is re-washed for future use.