This may be due to differences in lab testing equipment, chemical reagents, and analysis techniques. This test does not give information about past infections or future immunity. Jones G, Barker A. Davis Company; 2000:10-17. Home. HCG pregnancy In the case of the nasopharyngeal swab RNA test for covid-19, the positive likelihood ratio is about 14, which is excellent.6 A positive covid-19 test result should be very compelling. Alkaline phosphatase (ALP), for instance, is an enzyme found in the cells that make bone, so its concentration in the body rises in proportion to new bone cell production. Of 129 eventually diagnosed with covid-19 by RT-PCR, 92 (71.3%) had a positive test on the first throat swab, equating to a sensitivity of 71% in this lower prevalence, community setting.12. Many other tests, however, are reported as numbers or values. But not everyone is typical. Understanding Your Test Results | Cologuard Patient Site Available from: FDA: U.S. Food and Drug Administration [Internet]. The negative likelihood ratio is 0.3, which is a moderate result, but not nearly as compelling as a positive result because of the moderate sensitivity (about 70%) of the covid-19 test. Reference values are the values expected for a healthy person. A positive COVID-19 PCR test means that SARS-CoV-2 is present. Nobody likes to get poked with a needle or pee in a cup. Sacher RA, McPherson RA, Campos J.Widmanns Clinical Interpretation of Laboratory Tests. Myth:If all my test results are within range, I have nothing to worry about.. If you did not have symptoms at the time of your PCR nasal swab, you may return to work in 10 days (provided you do not have a fever 3 days prior to return to work). The Chinese handbook of covid-19 prevention and treatment states if the nucleic acid test is negative at the beginning, samples should continue to be collected and tested on subsequent days.20 False negatives carry substantial risks; patients may be moved into non-covid-19 wards leading to spread of hospital acquired covid-19 infection,21 carers could spread infection to vulnerable dependents, and healthcare workers risk spreading covid-19 to multiple vulnerable individuals. The short answer to this question is by testing a large number of people who have key similarities and observing what appears to be typical for them. Overview of Testing for SARS What does it mean for a COVID test to say that the value is For example, pregnancy changes many aspects of a womans body chemistry, so what is typical for pregnant women is not typical for those who are not pregnant. Leukocyte in urine without nitrite If the leukocyte esterase test is positive and nitrite is Fecal Immunochemical Test (FIT): common questions A positive result means the test detected altered DNA and/or blood that could be caused by a precancerous polyp or colon cancer. Available from: National Cancer Institute [Internet]. Common Lab Tests; [cited 2018 Jun 19]; [about 4 screens]. Some reports include critical values that represent potentially life-threatening abnormalities. Graham Jones, Antony Barker. Accessed August 2015. The Elecsys anti-SARS-CoV-2 S assay exhibited its highest sensitivity (84.0%) at 15 to 30 days post-PCR positivity and exhibited no cross-reactivity, a specificity and PPV of 100%, and an NPV between 98.3% and 99.8% at 14 days post-PCR positivity, depending on the seroprevalence estimate. Sensitivity and specificity can be confusing terms that may be misunderstood14 (see supplementary file Definitions and formulae for calculating measures of test accuracy). Your provider will likely include a physical exam, health history, and other tests and procedures to help guide diagnosis and treatment decisions. To evaluate whether your numbers are within normal limits, it is best to refer to the reference range printed on the report you receive from the laboratory that performed your tests. These numbers dont mean anything on their own, so you have to see how yours compare to a healthy range called your reference range or reference value. Youll see this range on the lab test results. 2008;29 (Suppl i):S93-S97. However, your health care provider may want to conduct follow-up tests some months later to make sure youre still on track and to document any trends. Verywell Health's content is for informational and educational purposes only. Had a positive test result followed by a negative result. Before you leave your doctors office, ask when youll know the results.