An inconclusive COVID test result means the laboratory or testing device could not definitively determine if the SARS-CoV-2 virus was present in the sample. Unlike a clear positive or negative, the test returned an ambiguous finding, suggesting the possibility of infection without confirming it. Understanding this result is the first step toward taking appropriate public health measures.
Defining Inconclusive Results
An inconclusive result indicates that the test was run successfully but failed to meet the rigorous criteria for either a positive or a negative diagnosis. For molecular tests, like the polymerase chain reaction (PCR) test, this often happens when not all of the targeted viral genes are detected, or the amount of detected genetic material is extremely low. The test was unable to cross the threshold required to confidently label the sample as containing the virus or being completely free of it.
This status differs from an “invalid” result, which means the test failed entirely and did not work as intended. An invalid result usually occurs when the internal control mechanism of the test—designed to ensure the sample was collected and processed correctly—does not register. In contrast, an inconclusive result suggests the test stopped short of a definitive conclusion. The ambiguity of the inconclusive result means it should not be interpreted as a negative finding.
The Primary Causes of an Inconclusive Test
One frequent reason for an inconclusive result is a low viral load, which refers to the concentration of the virus in the sample. This low concentration often occurs when a person is tested very early in the infection cycle, or very late, when the body is clearing the infection. The test’s sensitivity is high, but the amount of viral genetic material, measured by a metric called the Cycle Threshold (Ct) value, is too faint to be called a confident positive.
The quality of the collected specimen is another major factor contributing to an ambiguous result. If the nasal or throat swab was not performed with sufficient depth or material, the lab may not have enough cells to reliably analyze. Poor sample handling, such as improper storage conditions or delays in transport, can also degrade the integrity of the viral material, leading to an indeterminate reading.
Finally, technical issues with the assay itself can cause an inconclusive result. This can include the presence of substances in the sample that inhibit the chemical reaction needed to amplify the virus’s genetic material, known as reaction inhibitors. For PCR tests that look for multiple viral gene targets, an inconclusive result is triggered when only one of the targets is detected, preventing the test from meeting the requirement for a full positive diagnosis.
Immediate Steps Following an Inconclusive Result
Upon receiving an inconclusive result, the immediate step is to act as if the result were positive until proven otherwise. This requires the person to immediately begin self-isolation to prevent potential spread to others. Isolation guidelines typically mean staying home and separating from other household members, especially those who are at higher risk for severe illness.
This presumptive positive status requires rigorous adherence to public health measures in the interim. Interactions with others should involve strict masking with a high-quality mask and meticulous hand hygiene. Individuals must also inform close contacts, work, or school about the ambiguous result and their decision to isolate. The most important action is to contact the healthcare provider or testing site right away to schedule a follow-up test.
Understanding Retesting and Final Diagnosis
The resolution of an inconclusive result almost always requires a second test to establish a definitive diagnosis. Healthcare providers generally recommend a repeat test using a highly sensitive molecular method, such as a laboratory-based PCR test, collected 24 to 48 hours after the initial sample. This brief waiting period allows the viral load to increase, if the person is truly in the early stages of infection, thereby improving the chance of a clear positive or negative result.
The final diagnosis relies on the outcome of this retest and the presence or absence of symptoms. If the follow-up test is negative, the person can end isolation, provided their symptoms have resolved. If the retest is positive, or if the individual is symptomatic even with a negative result, they must continue to follow isolation protocols. In rare cases, a second test may also return an inconclusive result, necessitating further consultation with a medical professional.