Karlsson will have a 1.5 minute lead overall after four of seven stages.
In today's race, she finished 14 seconds ahead of Pärmäkoski after a tactically perfect effort.
It was a completely different scenario than in the men's race, where a cluster of 30 men went together at the end.
On the fifth lap (out of six) there was panic among the Swedish leaders because Karlsson did not know which lap she was on.
Karlsson, who went out first, had decided to drive on at a tightly controlled pace in order not to offer anything to the trio of Krista Pärmäskoski, Anne Kjersti Kalvå and Tiril Udnes Weng, who went out 16-20 seconds behind at the start.
A quartet after 6.6 km
After 6.6 km, however, Karlsson was caught up and the lead was a quartet.
After eleven kilometres, Kalvå, who had to let go several times, had to let go definitively and there were three left in the lead.
Shortly afterwards, it was World Cup leader Udnes Weng's turn to give up.
Today's start times were based on yesterday's results in the classic race over 10 km with an individual start - and not on the overall standings.
Results of today's race.