<p>A sudden surge in the number of novel coronavirus cases in China has put a spotlight on the ways patients are tested for the illness, from lung imaging to uncomfortable lab tests that are not always accurate.</p>.<p>On Thursday, China saw its largest one-day jump in confirmed cases -- adding over 15,000 -- after health officials in Hubei province, the epicentre of the outbreak, changed their counting criteria to include those "clinically diagnosed".</p>.<p>Here's a look at what that means and how testing for the COVID-19 illness works in China:</p>.<p>In China, the main way to test patients is using the Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) technique.</p>.<p>RT-PCR tests can detect the new coronavirus in patient blood or respiratory tract samples, including those taken from the nose or throat.</p>.<p>In a video released last week by a hospital in Wuhan -- the quarantined city where the virus first emerged -- medical staff demonstrated how to retrieve samples from a patient's nose.</p>.<p>Inserting a stick deep inside her colleague's nostril, one of the women instructed viewers to move the instrument in clockwise and counterclockwise circles.</p>.<p>The depth should be "halfway between the tip of the nose and earlobe", she explained, as the mock patient's eyes pinched shut.</p>.<p>Once samples are collected, they are sent to labs and processed in batches.</p>.<p>Zhang Hongxing, head of Wuhan's health commission, said last week the city tested about 6,000 to 8,000 people daily.</p>.<p>Besides nucleic acid tests, another method to confirm cases uses genetic sequencing, according to guidelines released by China's National Health Commission.</p>.<p>Patients test positively if the genetic sequence of their blood or respiratory tract sample has a "high degree" of similarity with that of the virus.</p>.<p>Not everyone can be tested for the illness -- patients have to be marked as a "suspected case" first.</p>.<p>To be counted as a suspected case, individuals have to check several boxes, including symptoms and travel history.</p>.<p>Anyone who has travelled to Wuhan or neighbouring areas are considered more likely to be infected, according to NHC guidelines.</p>.<p>Those who have had contact with confirmed COVID-19 patients or Wuhan visitors with a fever are also higher risk.</p>.<p>"Suspected" patients can also show symptoms linked to the new coronavirus, such as a fever or low white blood cell count.</p>.<p>Apart from lab-based tests like RT-PCR kits, Hubei health officials are also using lung imaging to "clinically diagnose" patients.</p>.<p>If lung images show pneumonia, patients who are already marked as suspected cases are confirmed as infected without the need for a positive RT-PCR test.</p>.<p>As of Saturday, around 17,000 people were clinically diagnosed in Hubei.</p>.<p>The goal is to "facilitate early diagnosis, early treatment... and improve the success rate of treatment," said Zeng Yixin, vice minister at the NHC at a press conference Friday.</p>.<p>No other provinces have adopted Hubei's standard, he added.</p>.<p>"It's a very interesting and logical approach," said Jessica Justman, associate professor of medicine in epidemiology at Columbia University.</p>.<p>Using lung images only works for "people with more advanced symptoms", she told AFP, which means it would not be used to screen patients early on.</p>.<p>But for those later-stage individuals, if there is no access to RT-PCR tests "it makes sense", said Justman.</p>.<p>Testing capacity remains a challenge in China, said experts, especially as the number of cases continues to soar while researchers race to develop faster and more accurate tests.</p>.<p>Laboratory tests like RT-PCR require special equipment, a clean environment, and "highly skilled staff", said Justman, to prevent samples from becoming contaminated.</p>.<p>The genetic sequencing option is also not "widely available", she explained. "For now it is an exciting but costly 'high tech' approach and interpretation of the results can be complex."</p>.<p>To mitigate this issue, Hubei province -- which accounts for 82 percent of nationwide cases -- has received reinforcements from other regions and China's centre for disease control to process nucleic acid tests.</p>.<p>Another issue with current tests is speed -- RT-PCR tests can take two to three hours, said John Nicholls, clinical professor in pathology at the University of Hong Kong.</p>.<p>And if hospitals have a limited daily capacity to run tests, that in turn becomes a "ceiling" for monitoring the spread of the epidemic, said Ben Cowling from Hong Kong University's School of Public Health.</p>.<p>Finally, RT-PCR kits can result in false negatives for a variety of reasons, including issues with the kits themselves, the technicians, or improper sample collection, said Cowling.</p>.<p>"No test is totally accurate," added Nicholls. That's why testing is "very much an area that needs improvement".</p>
<p>A sudden surge in the number of novel coronavirus cases in China has put a spotlight on the ways patients are tested for the illness, from lung imaging to uncomfortable lab tests that are not always accurate.</p>.<p>On Thursday, China saw its largest one-day jump in confirmed cases -- adding over 15,000 -- after health officials in Hubei province, the epicentre of the outbreak, changed their counting criteria to include those "clinically diagnosed".</p>.<p>Here's a look at what that means and how testing for the COVID-19 illness works in China:</p>.<p>In China, the main way to test patients is using the Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) technique.</p>.<p>RT-PCR tests can detect the new coronavirus in patient blood or respiratory tract samples, including those taken from the nose or throat.</p>.<p>In a video released last week by a hospital in Wuhan -- the quarantined city where the virus first emerged -- medical staff demonstrated how to retrieve samples from a patient's nose.</p>.<p>Inserting a stick deep inside her colleague's nostril, one of the women instructed viewers to move the instrument in clockwise and counterclockwise circles.</p>.<p>The depth should be "halfway between the tip of the nose and earlobe", she explained, as the mock patient's eyes pinched shut.</p>.<p>Once samples are collected, they are sent to labs and processed in batches.</p>.<p>Zhang Hongxing, head of Wuhan's health commission, said last week the city tested about 6,000 to 8,000 people daily.</p>.<p>Besides nucleic acid tests, another method to confirm cases uses genetic sequencing, according to guidelines released by China's National Health Commission.</p>.<p>Patients test positively if the genetic sequence of their blood or respiratory tract sample has a "high degree" of similarity with that of the virus.</p>.<p>Not everyone can be tested for the illness -- patients have to be marked as a "suspected case" first.</p>.<p>To be counted as a suspected case, individuals have to check several boxes, including symptoms and travel history.</p>.<p>Anyone who has travelled to Wuhan or neighbouring areas are considered more likely to be infected, according to NHC guidelines.</p>.<p>Those who have had contact with confirmed COVID-19 patients or Wuhan visitors with a fever are also higher risk.</p>.<p>"Suspected" patients can also show symptoms linked to the new coronavirus, such as a fever or low white blood cell count.</p>.<p>Apart from lab-based tests like RT-PCR kits, Hubei health officials are also using lung imaging to "clinically diagnose" patients.</p>.<p>If lung images show pneumonia, patients who are already marked as suspected cases are confirmed as infected without the need for a positive RT-PCR test.</p>.<p>As of Saturday, around 17,000 people were clinically diagnosed in Hubei.</p>.<p>The goal is to "facilitate early diagnosis, early treatment... and improve the success rate of treatment," said Zeng Yixin, vice minister at the NHC at a press conference Friday.</p>.<p>No other provinces have adopted Hubei's standard, he added.</p>.<p>"It's a very interesting and logical approach," said Jessica Justman, associate professor of medicine in epidemiology at Columbia University.</p>.<p>Using lung images only works for "people with more advanced symptoms", she told AFP, which means it would not be used to screen patients early on.</p>.<p>But for those later-stage individuals, if there is no access to RT-PCR tests "it makes sense", said Justman.</p>.<p>Testing capacity remains a challenge in China, said experts, especially as the number of cases continues to soar while researchers race to develop faster and more accurate tests.</p>.<p>Laboratory tests like RT-PCR require special equipment, a clean environment, and "highly skilled staff", said Justman, to prevent samples from becoming contaminated.</p>.<p>The genetic sequencing option is also not "widely available", she explained. "For now it is an exciting but costly 'high tech' approach and interpretation of the results can be complex."</p>.<p>To mitigate this issue, Hubei province -- which accounts for 82 percent of nationwide cases -- has received reinforcements from other regions and China's centre for disease control to process nucleic acid tests.</p>.<p>Another issue with current tests is speed -- RT-PCR tests can take two to three hours, said John Nicholls, clinical professor in pathology at the University of Hong Kong.</p>.<p>And if hospitals have a limited daily capacity to run tests, that in turn becomes a "ceiling" for monitoring the spread of the epidemic, said Ben Cowling from Hong Kong University's School of Public Health.</p>.<p>Finally, RT-PCR kits can result in false negatives for a variety of reasons, including issues with the kits themselves, the technicians, or improper sample collection, said Cowling.</p>.<p>"No test is totally accurate," added Nicholls. That's why testing is "very much an area that needs improvement".</p>