The U.S. Food and Drug Administration has issued another recall Class I for Celltrion's DiaTrust COVID-19 Ag Rapid Test diagnostic kit distributed in the U.S, making it the third such order from the regulator in less than two months.

The Class I recall is the most serious type of recall issued by the FDA and is for the use of devices that may cause serious injuries or death.

The FDA has authorized the kit only for use at the point of care. It requires a nasopharyngeal sample collected by a healthcare provider and sent to a clinical laboratory improvement amendments (CLIA)-certified laboratory for processing.

The U.S. agency issued the recall order the kit may have been distributed to unauthorized users.

"Emergency use of these tests is limited to authorized laboratories, and use of these tests in unauthorized settings may present an increased risk of false results as the persons performing these tests may not have the qualifications or training to properly and safely administer them," the FDA said in its recall notice.

Although there have been no reports of injuries, adverse health consequences, or death associated with using these affected products, false positive or false negative results from improper use of these tests could lead to the further exposure of uninfected individuals to the Covid-19 virus, the FDA added.

The agency also stressed serious injury risks if someone without the proper training tries to collect a nasopharyngeal swab sample.

The recall affects 311,100 units distributed around the U.S. in the three months between December and February.

Following the FDA recall order, Celltrion USA notified customers about this issue by email. It instructed them to provide a CLIA Certificate Number and contact information to their distributor on April 5.

The company also instructed customers without CLIA certification not to use any test kits currently in inventory, quarantine them, and return the product to the distributor, along with an acknowledgment and receipt form attached to the email.

"This is a case where a primary distributor purchased the kit, approved only for CLIA-certified laboratories and institutions, from Celltrion USA and sold them to secondary or tertiary distributors who do not have a CLIA ID," a company official said to Korea Biomedical Review on Monday. "However, only a small portion of the total distribution was subjected to the recall."

Celltrion USA and its distributors are currently faithfully carrying out recalls under FDA guidelines and have mostly completed the product recalls.

The most recent recall follows a recall of 119,600 units of Celltrion DiaTrust COVID-19 Ag Rapid Test diagnostic kit distributed in the U.S. on March 23.

The FDA ordered the recall as the diagnostic kits in distribution were for research use only (RUO) and not for commercial sale. Celltrion USA proceeded to recall the kits voluntarily, but the FDA assigned a Class 1 recall.

On March 22, the FDA also issued a recall for 45,500 units of Celltrion's product in the U.S. due to the possible discoveries of false-positive results of some products and an error in the expiration date description, and the possibility of false-positive detection.

Notably, the FDA found that the company had put the product's shelf life at 18 months, even though an emergency use approval gives a shelf life of 12 months.