COVID-19 TESTS: THE PROBLEMS OF FALSE-NEGATIVES AND FALSE-POSITIVES AND WHAT TO DO FOR IT?

 

RT-PCR is considered to be the reliable test presently to pick up cases and asymptomatic carriers of coronavirus. But these tests have their own fallacies. The false-negative rates vary from 2 to 33% while the false positive rates are anywhere between 0.2 to 4 %. Both conditions are unwelcome and have their own issues.

NEPAL AIRLINES AND ITS HONG KONG FLIGHTS PROBLEMS

Nepal Airlines had started its flights in the Kathmandu-Hong Kong sector. But on 3 October 2020, five passengers who allegedly were COVID-19 test negative in Kathmandu tested positive in Hong Kong on arrival. And Hong Kong banned the flights from Kathmandu for 2 weeks. It was unexplainable how these five people who had submitted negative results of COVID-19 done 72 hours before the flight tested positive in Hong Kong. Was it faking of results or false negativity of the reports? Or could it be due to these five getting a new infection after they had given samples for the testing within the 72 hours time frame? Or was it false-positivity in Hong Kong? There seem to be too much of ‘ors’ there!!!

Coronavirus, the mystery and challenge [Source: WHO]

An official for the national carrier said:

“After having conducted their PCR test, people are supposed to remain isolated and not come in contact with anybody but most of them tend to flout this protocol. This could be the reason why such a situation has occurred. Those five passengers must have come in contact with an asymptomatic COVID-19 patient after their PCR test was conducted,”

The flights resumed on 18 October and on 21 October, 9 passengers who tested negative on PCR in Kathmandu were found to be again positive in Hong Kong. And a ban was reimposed until 4 November 2020.

FALSE-NEGATIVES AND PROBLEMS

Having a false-negative report means the person is actually having the virus in him with or without symptoms but it has not been picked up in testing. Thus the person might be falsely assured of the absence of the virus in him or her. He or she might later have manifestations of the disease and even death. On the other hand, such a false-negative person might move around freely infecting others without realizing that he or she is the carrier of the infection and responsible for the transmission.

False-negative results of COVID-19 testing [Source: The ET]

This is risky for the family and society at large. And it would defeat the very purpose of testing and isolation. But it is happening and some systemic analysis has put these figures as high as 33%. This implies that of every 10 tests performed, 3 are falsely negative.

FALSE-POSITIVES AND PROBLEMS

This too is happening and means that a healthy person might get misdiagnosed as being carrying the infection. This too has serious consequences. It may lead to unnecessary isolation for the person with subsequent financial and work losses. Emotional trauma to the person and family are also immense. Dr Benjamin Mazer, a pathologist and diagnostics expert at Johns Hopkins University states:

“Although false positives may seem relatively harmless in comparison with their false-negative cousins, people can absolutely get hurt,” 

Some caregivers might have to be isolated from children and older family members due to such false-positive reports. It also incurs a financial burden on the health care system since the person might need to be put into a hospital or such facility for isolation. More tests later might be needed to be repeated to confirm whether the reports have turned negative or not.

Besides, if a person is healthy but needs to be isolated based on false-positive reports, he might be put in crowded areas where he might actually contract the virus and die. Thus we are pushing such a person to his death which is unethical and criminal.

The false-positives and false-negatives in coronavirus infection results explained [Source: The Conversation]

Also, such a person may end up with unnecessary treatment and their side-effects. No test is perfect. Hence people should be made aware that the tests have their limitations. Besides, labs should do their own external and internal audit of their tests. Also, pretest probability should be considered before we decide to put a false-positive person in quarantine based on the reports. His previous history of covid-19, antibodies, contact with cases, and symptoms should be taken into account. Besides, an alternative diagnosis should also be considered in light of the reports. All this will help to lessen the possibility of false-positive reports.