Six items of respiratory diseases

The six frequently asked questions about respiratory diseases are currently the most commonly used rapid respiratory infection screening combination in primary hospitals, outpatient and emergency departments. The routine test items are Mycoplasma pneumoniae IgM, Chlamydia pneumoniae IgM, respiratory syncytial virus IgM, adenovirus IgM, and influenza A virus I. gM, influenza B virus IgM, the core value is to produce results in 1-2 hours, quickly distinguish the source of infection, and avoid blind use of antibiotics. The screening accuracy for patients with fever and cough lasting more than 3 days is about 75%. Ordinary people without respiratory symptoms do not need routine screening at all.

Last week, my sister's 3-year-old boy had a fever of 39.2 degrees and coughed so much that he spurted out the milk he drank. He went to the community hospital overnight. The doctor did not say anything and took a fingertip blood test for six tests. The results came out in 20 minutes and only showed a positive IgM for Mycoplasma pneumoniae. He directly prescribed azithromycin suspension without even prescribing cephalosporin. The fever subsided after two days of taking it home. In previous years, when the information was not so transparent, he might have had to inject the solution for two days to test the effect.

But if you think that these six items are a "universal screening package for respiratory tract infections", you are wrong. There is really a lot of controversy about this combination in the industry. Many respiratory doctors in tertiary hospitals feel that this combination was established ten years ago and has been unable to keep up with current clinical needs - just take Chlamydia pneumoniae. The proportion of adults infected now is less than 5%. In many cases, weak positives are detected, which are either cross-reactions from previous infections or false positives. The reference significance is very small, but it is easy to mislead people into over-medication. Therefore, many places have now replaced the chlamydia pneumoniae in the six items with the new coronavirus or parainfluenza virus, or even directly split it into a flexible combination of three or four items. For children, the focus is on checking for mycoplasma, syncytial virus, adenovirus, and influenza, while for adults, testing for influenza A and B plus mycoplasma is more cost-effective.

Many people around me go to the hospital and ask for six prescriptions when they have a cough for more than a week, saying they want to check if there is any major problem. In fact, there is really no need to rush. You have to know that these six tests are all IgM antibodies, which can only be measured in the body 3-7 days after infection. If you go for the test on the first day when you have a fever, it will most likely be a false negative, and it will be a waste of money. For some people, IgM can stay in the body for a month or two after the infection is cured. If you check out positive at this time and think you are infected again, you are just scaring yourself. I asked an old classmate in the respiratory department for a friend before, and he said that they now ask about the course of the disease before prescribing this test. For those who are within 3 days of the onset of illness, priority is given to rapid antigen tests for individual pathogens, such as throat swabs for influenza A and mycoplasma. The results are available in 15 minutes and are more accurate than six tests. For those who have been ill for more than 3 days and have recurring fevers and severe coughs, six more tests will increase the accuracy by more than 20%.

Nowadays, many people on the Internet are criticizing this six-item test for being inaccurate, saying that their test results were all negative, but the nucleic acid test showed that they were positive for mycoplasma. This really cannot be entirely blamed on the test itself. The sensitivity of antibody detection is inherently lower than that of nucleic acid. Especially for some elderly people with low immunity and people who have taken hormones for a long time, antibodies are produced slowly or even not at all, so naturally they cannot be detected. The industry is now divided into two groups. One group believes that the six-item test is suitable for primary screening at the grassroots level. It is cheap and provides quick results and can solve 80% of common problems. The other group believes that direct nucleic acid joint testing is more accurate, but it is more expensive. A set costs 300 yuan less. Ordinary families may be reluctant to part with it. To put it bluntly, it is a trade-off between cost and efficiency, and there is no absolute right or wrong.

A while ago, when the flu was at its peak, I was browsing Xiaohongshu and saw many people posting their six-item report sheets. They were all negative but coughed so hard that their lungs were coming out. I was worried about whether I had pneumonia. In fact, this high probability is caused by rhinovirus and human metapneumovirus, which are not included in the six pathogens. They are inherently self-limiting. Just take some cough medicine and get over it. There is no need to infuse infusions and take antibiotics because the pathogen cannot be found.

To be honest, we ordinary people don’t need to think too deeply about these six items. It is just a tool to help doctors quickly narrow the scope of infection. There is no need to deify or step on it. When it is time to check, listen to the doctor. If you don’t have symptoms, don’t join in the excitement of this “full set of tests”.