FAST FACTS: Steps in a coronavirus PCR-based test

MANILA, Philippines – As the Philippines continues its fight against the novel coronavirus, the government has ramped up its efforts by placing the entire island of Luzon on lockdown and expanding the country’s capacity to test more people for possible infection.

As of Thursday, April 2, the Philippines had 2,633 confirmed cases of the coronavirus disease, with 107 deaths, and 51 recoveries. The global death toll reached more than 47,000 and infected more than 900,000. 

The Department of Health (DOH) earlier said that the public could expect a spike in the number of confirmed cases as they work on their backlog of tests. 

Health experts estimated that the number of cases in the country may reach anywhere between 26,000 to 75,000. (READ: Ex-DOH chief: Actual number of virus cases could reach 75,000 in 2 weeks)

On Thursday evening, April 2, government said it is planning to begin "massive testing" for persons under monitoring and patients under investigation for the coronavirus disease (COVID-19). 

According to Secretary Carlito Galvez Jr, National Task Force (NTF) COVID-19 chief implementer, the objective is to identify as many carriers of the virus as possible and isolate them. (READ: ‘Massive testing’ of coronavirus PUMs, PUIs to start April 14 – Galvez)

How does a coronavirus test kit work?

The most popular testing method for coronavirus in the Philippines is the polymerase chain reaction or PCR-based test which uses actual swabs from patients to determine the presence of the coronavirus.

On March 30, the Food and Drug Adminsitration (FDA) approved the use of rapid test kits which require the patient's blood sample and can only detect antibodies.

While rapid test kits will yield faster results compared to PCR-based test kits, a patient’s swab will still be taken for confirmatory testing using the standards of the latter (PCR). 

Here’s how the PCR-based test is being done at the Research Institute for Tropical Medicine (RITM) – the Philippines’ national reference laboratory for infectious and tropical diseases:

STEP 1: RECEIVING

Swabs delivered to the laboratory are assessed if they adhere to the appropriate collection, handling, and transport criteria. According to the RITM, the specimen should come with a Case Investigation Form and Laboratory Request Form.

STEP 2: ENCODING

Data pertaining to the samples are encoded into the Laboratory Information System and in the sample monitoring program. Afterwards, the samples are brought to the Special Pathogens Laboratory (SPL) which should be a Biosafety Level 2+ facility. (READ: RITM urges 'utmost diligence' in setting up coronavirus testing centers)

STEP 3: INACTIVATING 

Once the specimen arrives at the SPL, the virus is inactivated. This means that the ability of the virus to infect will be removed. According to the World Health Organization, inactivation means the virus is "lysed, fixed or treated to prevent contamination."

STEP 4: REAGENT PREPPING

This is when the enzymes, primers, and probes are prepared for the first screening.

STEP 5: SCREENING

At this stage, the presence of the coronavirus is determined. 

STEP 6: CONFIRMING TEST

If the sample tests positive for the virus, it is subjected to a confirmatory test. To ensure accuracy, steps 5 and 6 use positive and negative controls.

STEP 7: VALIDATING

After the screening and confirmatory tests, the sample undergoes validation.

STEP 8: RELEASING

The results are released to the Regional Epidemiology Surveillance Unit that is in charge of forwarding them to hospitals.

The RITM said that turnaround time for the confirmation of coronavirus results is 48 hours. However, there are instances when the samples received by the laboratory don't meet the criteria for acceptable specimen, adding to processing time. – Rappler.com

Bonz Magsambol

Bonz Magsambol is a multimedia reporter for Rappler, covering health, education, and social welfare. He first joined Rappler as a social media producer in 2016.

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