When SARS-CoV-2 Infection started, a lot of people didn’t even know that there’s this term called the “Rapid Test Kit”. What it simply means is that the kit is specifically designed to provide a result of whether a person is positive/negative, depending on what the test kit is designed to measure, without needing to go to the doctor. The most common that we know of is the Pregnancy Test kit.
During the early days of Covid, the only way to check if a person is infected with the virus is through the RT-PCR test. It is the most accurate way of confirmation so far, but it comes as a big cost and a bis discomfort as each test requires the patient to do a nasal swab. On Average, each test takes more than 24 hours for the result to be out. Not to mention the price is well above >RM300 when the test is first offered in the private hospitals throughout Malaysia.
Thanks to a better understanding of the SARs-COV-2 antigen, medical labs are able to create rapid antigen test kits that are used at the point of care. The early rapid tests still also use a Nasopharyngeal swab to collect samples, but the screening time has definitely reduced to only about 2-3 hours, and the price is also in the RM200 range (Still cheaper than RT-PCR).
It is not until Mid 2021 that a rapid test kit/home test kit starts appearing. This Covid-19 test kit makes testing even easier by allowing the suspected person to do it himself/herself using a saliva sample. No more trips to the hospital (unless to get an RT-PCR diagnostic test).
To make these home test kits affordable, the government has announced that the ceiling price will be set at RM39.90 per unit. There are still calls from the opposition to make the test kit even lower price so that it is even more affordable for the general public, especially the B40 and M40 segments.
On the 2nd September 2021, the government has announced that the new ceiling price for Home Test Kits will be RM19.90 moving forward. The wholesale price is also set at RM16. Though this move is widely lauded by the public for the decrease in price, it has caused the pharmacies and clinics to be in limbo as they have old stocks that are purchased at a much higher price, but they have to follow suit with the ceiling price. The new price will be effective from the 5th September onwards.
So, how to measure a test kit’s accuracy?
To put it in plain terms, Accuracy is a combination of Sensitivity and Specificity.
Sensitivity – refers to the proportion of those who have the condition (when judged by the ‘Gold Standard’) that received a positive result on this test. – Wikipedia
Specificity – refers to the proportion of those who do not have the condition (when judged by the ‘Gold Standard’) that received a negative result on this test. – Wikipedia
In Layman Terms:
Sensitivity – How many sick people is correctly identified as really having an active infection and not due to false positive
Specificity – How many healthy people is correctly identified as not having the condition and not due to false negative
We can check from the white paper that each self-test kits publish, about the tests that they did to measure the accuracy of their own devices, often comparing it with the RT-PCR test, which is the “confirmatory tests”.
|Self Test Kit||Positive||Negative||Total|
Out of the 112 Tested positive for RT-PCR diagnostic test, Self Test kit only picks up 109, that is 109/112 = 97.3%
Out of the 97 Tested negatives for RT-PCR diagnostic test, Self Test kit managed to identify 96, so 96/97 = 99.0%
So the Accuracy of the test can be determined to be (97.3%+99.0%)/2 = 98.15% (Estimate)
It is by these measures of accuracy, that Rapid Covid-19 tests can be deployed as a mass screening test, as the time taken is short (Average 15 minutes across most brands).
What is the baseline for the test kit that can be approved for conditional approval by MDA?
Though not specifically mentioned on their website, Dato Norhisham did give an indication that for MDA to grant approval. In Malaysia, the Rapid Covid-19 Test Kit’s sensitivity must be above 80% and the Specificity must be above 97%.
What are the Sensitivity, Specificity and Accuracy of the Covid-19 Rapid Antigen Test approved by the MDA?
I saw other brands not listed in the MDA-approved list. But the Sensitivity and Specificity shared by the seller are quite high, can I trust them?
Always do your due diligence when using brands that is not MDA approved. Though the cost of the test kit is a concern (most of the not approved test kits are way cheaper), there is always an ethical concern if the results supplied by the manufacturing company are true. For MDA approved test, they will conduct the testing again in Malaysia to support the claim, hence the accuracy of the test kit is of utmost importance.
There is always a fear of false-negative for unapproved test kits. The asymptomatic patient is Covid Positive, but the test kit reports as negative. If this patient assumes he/she is safe and continues to wander around, it could cause a new cluster forming, due to a faulty test kit.