Some testers gently swab the front of your nostril and send you on your way. Others dig deep, bringing the pain. What’s the gold standard?One Canadian said it felt like a painful poke to his brain. An American heard crunching sounds in her head. A Frenchwoman suffered a severe nosebleed. Others got headaches, cried or were left in shock.They were all tested for Covid-19 with deep nasal swabs. While many people have no complaints about their experience, for some, the swab test — a vital tool in the global battle against the coronavirus — engenders visceral dislike, severe squirming or buckled knees.“It felt like someone was going right into the reset button of my brain to switch something over,” Paul Chin, a music producer and DJ in Toronto, said of his nasal swab test. “There’s truly nothing like it.”“Oh, my goodness,” he continued, “the swab just going farther back into my nose than I’d ever imagined or would have guessed — it’s such a long and sharp and pointy kind of thing.”Since the coronavirus emerged, millions of swabs have been stuck into millions of noses to test for a pernicious virus that has killed millions across the planet. One of the ways to fight the virus, officials say, is to test widely and to test often. The imperative has been to use a test that people are willing to take repeatedly.The swab generally fits the bill.In some parts of the United States, health workers hand people the swab to test themselves, assuring a level of personal comfort. To many South Africans, the only Covid-19 test is a painful one — you see stars or gag because a nasal swab goes down your throat.The range of swabbing raises questions: Who is doing it right? How deeply should the swab slide into your nostril? How long should it spend up there? Does an accurate test have to be uncomfortable? Unfairly or not, some countries have reputations for brutal tests.First, a brief anatomy lesson: No, the swab is not actually stabbing your brain.