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Test criteria for coronavirus
The following should be tested:
- Everyone with acute respiratory tract infection or other symptoms of COVID-19
- Everyone who has been exposed to infection to COVID-19, either as a close contact or after travel to countries or regions with high incidence during the last 10 days.*
- Personnel in nursing homes **
- Other groups can be tested after assessment by a doctor.
- Anyone who suspects that they have COVID-19 should have the opportunity to be tested
*Children play a smaller role in transmission of COVID-19 than adults, so testing of children of primary school or child care age will therefore be of less significance. However, testing can be carried out in relation to contact tracing and in consultation with parents/guardians.
** Nursing home personnel shall always have a low threshold for being tested according to criterion 1 and/ or 2 above. In municipalities with very high transmission, we recommend that nursing homes offer regular screening of personnel before starting to work there, and then once a week, so that infection is detected early. Similarly, testing is recommended before starting to work there and after 7 days for personnel who have been in these areas with high transmission levels during the last 10 days. Personnel can work while waiting for test results
When people without symptoms and who are not exposed to infection are tested, positive test results should be confirmed by a new test.
The doctor at the test centre is responsible for informing the patient and their regular doctor of the test result (both positive and negative test results), and for notifying the Norwegian Surveillance System for Communicable Diseases (MSIS) of any positive results on the same day they are available. Electronic MSIS notifications can be sent by a doctor, or by a nurse on behalf of a doctor.
Supplementary information about who should be tested
1) Test of everyone with symptoms of COVID-19
The Norwegian Institute of Public Health recommends that everyone with symptoms of COVID-19 should be tested as soon as possible.
This includes anyone with a newly arisen respiratory tract infection or other symptoms of COVID-19. COVID-19 often has the following symptoms; fever, cough, shortness of breath, loss of taste or smell, sore throat, or feeling unwell.
For residents of nursing homes, there should be an extremely low threshold for suspicion of COVID-19.
Children under the age of 10 with only mild symptoms of respiratory tract infection can be observed at home for a few days before testing. Children with a runny nose as the only symptom, who are otherwise in general good health without other signs of a newly arisen respiratory tract infection, do not need to be kept at home or tested.
Everyone who is tested should stay at home until a negative test result is available. With a negative test, they can return to work/school when their general condition is good (they feel well and have no fever), even though they still have a few symptoms after the respiratory tract infection.
For deaths in healthcare institutions where a doctor suspects that the patient had COVID-19, post mortem tests for COVID-19 should be performed.
2) Test of asymptomatic patients who have been exposed to COVID-19 infection
Anyone with a known exposure to COVID-19 infection within the last 10 days (close contacts, arrivals from high-incidence countries or other known exposure to confirmed cases) should be tested, even if they present no symptoms.
This includes the following groups:
- Close contacts of lower secondary school age and above who have been quarantined. They can be tested to speed up further contact tracing, but the test result will not affect quarantine time. Suggested test date to detect most cases; between day 3 and 7, preferably day 5.
- Some cross-border workers may be exempt from quarantine during working hours during testing, see the exemption provisions and test regime in §6b and 6c of the COVID-19 regulations. For personnel in critical functions in society who are covered by the exemption from the entry and infection quarantine mentioned in §6e, it is also strongly recommended, if possible, to carry out a test regime as described in §6c. The exemption can only be used in cases where it is necessary to avoid danger to life and health.
- If infection is detected in a nursing home, all employees and residents of the affected units should be tested.
- People arriving in Norway from areas or countries with a higher incidence of COVID-19 can be tested to speed up further contact tracing, but the test result will not affect time in quarantine.
There is usually no basis for forcing people without symptoms to be tested, according to the Infection Control Act.
3) Test of others after assessment by a doctor
In some situations, people should be tested even if they have neither symptoms of COVID-19 nor have a known exposure to the disease.
This includes the following groups:
- Employees in the healthcare system who work close to patients, including new employees and temporary staff who have been travelling outside Norway during the last 10 days, should be tested and not work close to patients until a negative test result is available.
- Before new residents move into a nursing home, testing may be appropriate and is recommended if the nursing home resident has been travelling outside Norway.
- Prior to certain hospital stays or procedures, testing may be appropriate. The hospitals themselves establish routines for this.
- The municipal medical officer may, in some cases, consider that there is an indication for testing before moving into / starting in particularly dense living environments or workplaces with a high risk of infection, e.g. arrival centres, military camps, slaughterhouses and prisons.
- Positive test results among asymptomatic, non-infected individuals should be confirmed by a new test to improve the positive predictive value, see below.
4) Others who want to be tested
Other people who want to be tested but who do not have symptoms and do not suspect that they are infected can also be tested if there is available capacity. The cost of the test will then usually not be covered by the public sector. This may, for example, apply for health certificates.
Positive test results among asymptomatic, non-infected individuals should be confirmed by a new test to improve the positive predictive value, see below.
Recommended order of priority with a lack of testing capacity
If there is a lack of testing capacity, groups should be tested in the following order of priority:
A) People with symptoms
- Patient in need of hospital admission
- Patient / resident in a nursing home or other healthcare institution
- Employee in the healthcare service with work that puts them in the vicinity of patients
- Person in a risk group, see risk groups and their relatives
- People who have been exposed to infection
- Other people with symptoms
B) People without symptoms who have been exposed to infection:
- Outbreak situations in healthcare institutions
- A close contact to a confirmed case of COVID-19
- Healthcare personnel with patient contact who has been abroad
- Person who has been in quarantine after travel
- On arrival from abroad
Waiting for test results
The main rule is that anyone who has been tested must stay at home until their test result becomes available. Household members do not have to be in quarantine, nor do household members who work in the healthcare service.
There are two exceptions to the main rule:
- People who have been tested even though they have no symptoms or have not been exposed to infection, do not have to stay at home awaiting a test result.
- People who are in quarantine who have symptoms compatible with COVID-19 are considered as "probable COVID-19" pending test results. This means that the person who is sick is in isolation and household members and equivalent close contacts are in quarantine until test results become available.
Interpreting the test results
The PCR-test for COVID-19 is a good test with very high specificity and good sensitivity. It is estimated that the clinical specificity is around 99.999 per cent and that the clinical sensitivity is around 80 per cent. The sensitivity of the test depends on which stage of the disease the infected person is and is highest in the days around the onset of symptoms. Then it is probably over 90%. In the majority of cases, the test results are reliable. However, no test is completely accurate and the result must be interpreted according to the probability that the person is infected.
If the test result is negative, and there is still a strong clinical suspicion of COVID-19, a new test should be taken.
In the current infection situation, the probability is high that a positive PCR test is correct, even in cases where the person has no symptoms or is a close contact, and does not need to be confirmed by a new test.
In the event of a known infection in recent months, a positive PCR test result must be interpreted with caution. This is because non-infectious virus residues (non-replicable RNA) can be detected by PCR for a long time (up to two to three months) after the person is no longer contagious. This should also be considered in case of a weakly positive result in an asymptomatic person without an increased risk of infection, as most of those with a weakly positive PCR (Ct value above 33) will be past the contagious period. A new PCR test and an antibody test can help to clarify where the person is in the course of the disease.
If reinfection is suspected, contact the NIPH for advice.
Negative test results from people with symptoms
The probability of a false negative analysis result should be considered based on whether the person is a known close contact, clinical suspicion, time since symptom onset and other test results such as CT-thorax.
- If there is clinical suspicion of COVID-19 and a negative test response, the person should be retested. With a pre-test probability of infection of 30 per cent, a new test will reduce the probability of false negative test results from 8 per cent to 1.7 per cent (at 80 per cent sensitivity of PCR test).
- Tests from other localisations such as BAL, saliva, should be considered.
Test results at helsenorge.no
As soon as coronavirus tests are analysed, the laboratory sends the test results to:
- NIPH laboratory database
- The doctor - the result is shown in the electronic summary care record that healthcare personnel can access on helsenorge.no
- The patient's test results page at helsenorge.no
The patient can log on to Helsenorge.no with electronic ID to see their test result.
Many viruses and bacteria can cause respiratory tract infections. In the search for the correct diagnosis, it may be necessary to request other tests in addition to SARS-CoV-2, as approved by the Ministry of Health and Care Services, see below. Analysis results from the additional tests will be available to the patient on the test results website on Helsenorge.no and for the doctor in the summary care record. It is important that the person ordering the tests should explain to the patient about the different tests that are being sent for analysis.
The following infectious agents are defined by the Ministry of Health and Care Services as COVID-19 related infectious agents. The list is updated as of 2nd July 2020, and will be continuously updated at helsenorge.no:
- SARS-CoV-2 antibodies
- Influenza A / Influenza B
- Parainfluenza virus
- RS virus (Respiratory syncytial virus)
- Human metapneumovirus
- Mycoplasma pneumonia
- Chlamydia pneumonia
- Bordetella pertussis (whooping cough)
About the solution:
- Information for healthcare personnel about test results in Summary care records (helsenorge.no) - in Norwegian
- Summary care records (helsenorge.no)
- Test results page (helsenorge.no)
Why is testing of people without symptoms and without exposure not usually recommended?
Even with unlimited access to tests, it will usually not be advisable to test people without symptoms and have not been exposed to infection.
This is because:
- A negative test can give a false sense of security. The test result only gives a snapshot of the situation. A person with a negative test result may be in the incubation phase and not yet be sick.
- A positive PCR result may show infection that has passed and is no longer contagious. The PCR test detects the virus's genetic material and does not distinguish between viral fragments and an infectious virus. Viral fragments may be present in the respiratory tract for weeks after the infection has passed.
- Increased probability of false positive analysis results where there is low transmission in society (low positive predictive value).
With a prevalence of 0.005 per cent (probable prevalence among people without symptoms in Norway today), the positive predictive value would be around 80 per cent. That is, 2 out of 10 who test positive are not infected with SARS-CoV-2 (false positive analysis result). If a new test is taken, the positive predictive value will improve to over 99.99 per cent.
- With low prevalence, on average, many tests need to be taken to find a true positive, see table below.
Prevalence in the population to be tested
Number who need to be tested to find one true positive case
Probability for a true positive result (positive predictive value)
Number of false positive analysis results expected per true positive analysis result
Figures 1 and 2 below show examples of testing of 100 000 individuals (without symptoms, not exposed, randomly selected) with a prevalence of 0.005 per cent and 3 per cent, respectively, and with clinical sensitivity of 80 per cent and specificity of 99.999 per cent.
Figure 1 and 2: The figures show that with low prevalence/ probability, false positive results are the biggest problem, whereas with high prevalence/ probability, false negative results are the biggest problem.
- Flowchart for COVID-19 testing for acute respiratory tract infections - the flowcharts shown earlier in the article can be downloaded.
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SARS-CoV-2 is the name of the virus that is causing the outbreak of COVID-19 disease.
The virus is related to another coronavirus that caused the SARS outbreak in 2002/2003 but is not the same virus.