World Rugby has approved an optional extension of the head injury assessment (HIA) process for the remainder of the English Premiership and Championship seasons.

The HIA period could now last as long as 13 minutes – but no fewer than 10 – to allow for the collection of in-game saliva samples as part of a major study into the diagnosis of concussion during matches.

The process involves players providing a two millilitre sample of saliva off-field, as well as follow-up saliva and urine samples.

And with World Rugby's approval, the HIA procedure could now last an extra three minutes.

"Player recruitment for this study has been excellent and samples are steadily coming in from the first five rounds of matches," said Rugby Football Union chief medical officer Simon Kemp.

Premiership Rugby's head of elite performance and player development Corin Palmer added: "This is an important and potentially impactful study which has the full support of our clubs.

"Premiership Rugby and our clubs welcome the flexibility shown in providing an optional period of time to ensure the accurate completion of the saliva samples alongside the HIA."