China is one of only a few countries that offer such house-call services, which can be booked on mobile phone apps and allow users to avoid long waits in crowded queues at test centres or hospitals, sometimes outside in the cold.

The emergence of on-call testing also partly reflects individual anxiety about transmission risks, even though China reports relatively few COVID-19 cases, as well as an expanding range of testing options available to Chinese consumers, depending on one's budget.

Ou Yang, who works in the auditing industry in southern Fujian province, said she opted for a 358 yuan ($56) on-call test after she initially booked a spot at a local hospital.

"It's much more expensive than normal tests ... but it's worth it," said Ou, whose sample was collected at her workplace. "I'd gone to the hospital and queued up, but there were so many people and they were standing really close to one another."

The cost is well above the 80 yuan charge for on-site tests at clinics, hospitals and third-party testing centres, although the price of on-call tests done by private testers can fall to as little as about 100 yuan a person for companies that arrange group tests for staff.

Other premium services include emergency testing, faster turnaround time, and deals bundled with other genetic tests.

Demand for coronavirus testing in general has picked up during the so-called Spring Festival travel rush, when millions return to their home provinces to celebrate the Lunar New Year.

Some 600 million tests could be administered on travellers to rural areas alone during the 40-day holiday travel season, according to one private estimate, offering a potential bounty for test providers.

People travelling across provinces to rural areas in particular must test negative before leaving or on arrival, with authorities worried about infections in regions where the ability to identify and trace transmissions is relatively weak. On arrival, returnees face up to two more rounds of tests.

SCRUTINY

Hangzhou-based Weimai Technology, a start-up running an online booking platform since January for on-call tests offered by third-party companies, told Reuters that its platform was receiving well over 10,000 orders a day.

Most were cheaper bulk orders by companies that bundled sample-taking for 20-50 people, but the platform was also receiving a small number of individual orders, a Weimai representative said.

The demand has also attracted some private health-care providers that arrange nurses to collect samples at homes or workplaces and deliver them to testing labs.

The premium services, still a niche industry compared to ordinary on-site tests, are starting to draw the attention of authorities.

A Beijing health official told reporters on Tuesday that agencies offering personalised services should give a detailed breakdown of prices.

An advertisement for an on-call test in Beijing on the Alipay mobile app states: "80 yuan testing fee, 208 yuan service fee."

A guideline issued on Monday by the National Health Commission (NHC), China's health authority, encourages test providers to offer the option of cheaper mixed-sample tests, where multiple samples are processed together.

Demand for testing has also become a profit growth driver for bigger listed Chinese companies such as Guangzhou Kingmed Diagnostics Group, which conducted over 30 million nucleic acid tests as of end-December.

Dian Diagnostics Group Co and BGI Genomics Co, which develop testing kits as well as offer testing services, also said COVID-19 related demand are major reasons for expected surges in their 2020 net profit.

($1 = 6.4358 Chinese yuan renminbi)

(Reporting by Roxanne Liu and Ryan Woo; editing by Richard Pullin)