S-gene dropout test proposed for international travellers

A BBMP health worker collecting a swab for the COVID-19 test, from travellers at KSRTC Kempegowda Bus Stand, in Bengaluru on Tuesday.

A BBMP health worker collecting a swab for the COVID-19 test, from travellers at KSRTC Kempegowda Bus Stand, in Bengaluru on Tuesday.

With a rise in the number of international travellers testing RT-PCR positive on arrival at the airport, the State’s Technical Advisory Committee (TAC) has recommended that the State should start using S-gene target failure (SGTF) test kits at the Bowring and Lady Curzon Medical College and Research Institute for probable diagnosis of Omicron.

TAC members, who deliberated on the SGTF screening at the committee’s 139th meeting held on Monday, recommended that the TaqPath ‘S’ gene COVID-19 diagnostic kit by Thermo Fisher should be procured in Bowring Hospital that has been designated as a dedicated Omicron facility. The Thermo Fisher TaqPath assay can be used as a proxy test for detecting the new variant, pending confirmation by genome sequencing, stated the TAC’s report.

“Those testing positive at the airport can be brought to Bowring Hospital for testing using SGTF. Those who are detected with S-gene dropout (the test takes about four hours) should be considered as probable Omicron cases and shifted to the designated Omicron ward for isolation and treatment. However, for final confirmation of Omicron, their samples should still be sent for genome sequencing, which is the gold standard,” the report stated.

Discharge as per protocol

“Even if the genome sequencing report is delayed, the patients considered as probable cases of Omicron can be discharged as per the guidelines on the 10th day and sent for further home quarantine. This should resolve conflicts with patients and avoid confusion at the treating hospital, whether government or private,” the report said.

Sources in the TAC said that at least two travellers from high-risk countries are testing positive at the airport by routine RT-PCR and express tests. On suspicion of Omicron they are shifted to Bowring Hospital or any designated private hospital for isolation and treatment. Simultaneously their samples are sent for genome sequencing and for confirmation of Omicron.

“The results of genome sequencing are getting delayed (about 10 days or more) due to waiting at the lab level as a minimum of 94 samples are required for sequencing. Moreover, only samples with a Cycle Threshold (CT) value of less than 25 are eligible for sequencing. This delay has led to restlessness among these Omicron-suspected patients, who are either asymptomatic or mildly symptomatic and hence recover quickly,” sources said.

“They also test negative for two consecutive RT-PCR tests done before discharge on the tenth day. As a result they allege that they are unnecessarily held back in the hospital waiting for their genome sequencing report. Besides, if they opt for treatment in a private hospital the cost of which has to be borne by the patients themselves, this extra stay is considered avoidable and the resultant expenditure wasteful,” sources said.

Recently, three contacts of India’s second Omicron patient, a 46-year-old government anaesthetist who did not have any travel history, were initially discharged after they tested negative. However, they were asked to come back to the hospital as their genome sequencing reports had not arrived. The three - all doctors - left the hospital the next day without informing the authorities as they ‘no longer wanted to stay in a COVID-19 ward after testing negative.” Following this conflict, the State Government released discharge guidelines for Omicron patients.

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Printable version | May 23, 2022 12:34:19 am |