Health Corner

COVID-19 Testing: Why It Matters and How It Works?

COVID-19 has become a global pandemic. Many confirmed cases have unknown sources, and research shows that patients may carry high viral loads even during the early stages of infection and remain asymptomatic for a long incubation period. This makes the virus easier to spread.

At present, there is no specific medication for COVID-19, and vaccines are still under development. The most effective way to control the outbreak is to identify and isolate asymptomatic (hidden) carriers as early as possible. Therefore, choosing a reliable testing method is essential.

Who Should Receive a COVID-19 Test?

A. Asymptomatic individuals who fear or suspect infection
B. High-risk groups such as the elderly or those with chronic illnesses
C. People with symptoms including fever and upper respiratory tract infection
D. Individuals currently under home quarantine

What Are the Current COVID-19 Testing Methods? 

There are two primary types of tests available. Members of the public can choose based on their situation and needs.

I. Viral Genetic Testing (RT-PCR)

Sample Type: Deep throat saliva or throat swab
Principle:
This test uses real-time reverse transcription polymerase chain reaction (RT-PCR) to detect viral RNA in the patient’s sample.
The method is highly sensitive—able to detect even trace amounts of viral RNA—and is considered the clinical standard for diagnosis.

Processing Time: Around 6 hours
Technology: Must be conducted by trained technicians in a laboratory
Accuracy: Very high (though it depends on proper sampling technique)
Cost: Relatively high
Usage:
Due to its precision and sensitivity, RT-PCR is the gold standard for clinical diagnosis.
It is available at all Virtus Medical Centres, the Department of Health, and private hospitals across Hong Kong.

II. Antibody Testing – Rapid Blood Test

Sample Type: Blood
Principle:
Detects antibodies (IgM and IgG) in the blood.
Using just one drop of blood, a positive result typically appears as two lines on the test strip.

Processing Time: About 15 minutes
Technology: Simple and can be performed at the testing site
Accuracy: High, but not suitable for early-phase diagnosis
Limitations:
Since antibodies take about seven days after infection to appear, false negatives may occur in early infections, leading to misdiagnosis.

Cost: Low
Usage:
Due to its speed and affordability, this test is widely used for large-scale screening.
Some clinics offer the rapid antibody test, and at-home versions are also sold online claiming high accuracy.
However, since such online products are not regulated, their hygiene standards and accuracy are uncertain.
It is advisable to consult a doctor before using home test kits, which should only be used as supplementary reference tools.

Source: Weifang Kong and Prachi P. Agarwal

Some patients show “ground-glass opacity” patterns in lung X-rays.
Both chest X-rays and low-dose CT scans can effectively improve diagnostic accuracy, increase efficiency, and help rule out related complications.

Reference:
Detection of 2019 novel coronavirus (2019-nCoV) in suspected human cases by RT-PCR
https://www.who.int/docs/default-source/coronaviruse/peiris-protocol-16-1-20.pdf?sfvrsn=af1aac73_4

Radiological findings from 81 patients with COVID-19 pneumonia in Wuhan, China: A descriptive study
(Heshui Shi, Xiaoyu Han, Nanchuan Jiang, Yukun Cao, Osamah Alwalid, Jin Gu, Yanqing Fan, Chuansheng Zheng)

The information provided on this page is for general reference only and does not replace medical advice from your doctor.

For any questions or personal health concerns, please consult your physician.
No responsibility will be taken for any omissions or inaccuracies in the above content.