The limitations of testing

I READ with interest about calls to the Malaysian government for more testing by some quarters. While this may be well-intentioned, we should be aware of the limitations of tests, particularly the specificity and sensitivity of a test. The specificity of a test is the ability of a test to label a patient without disease, negative, while sensitivity is the ability of a test to label a patient with disease, positive.

It is well established that the real time polymerase chain reaction (qPCR) test has a higher sensitivity and specificity than rapid test kits (RTK). However, even qPCR does not have a sensitivity or specificity of 100%. Factors affecting sensitivity or specificity include the skill of the technician, quality of sample collected and conditions of the machine. A test with a sensitivity or specificity above 95% is widely considered acceptable.