Does Long Covid Show Up on Tests?

The Covid-19 pandemic has caused a new worry called long Covid. Even after recovering from the initial infection, some people have symptoms that last for weeks or months. People are wondering how to detect long Covid and how it affects the body. It’s important to understand long Covid and how to diagnose it, so we can support and care for those affected.

Understanding Long Covid and its Diagnosis

The Fundamentals of Long Covid

Long Covid symptoms can last even if a person tests negative for Covid-19 but shows T cell or antibody responses to the virus. This means that many cases of Long Covid might have been missed because patients didn’t get an official Covid-19 diagnosis.

A study in Neurology discovered that 41% of patients with Long Covid symptoms had T cell or antibody responses to the virus, even though they tested negative. This suggests that mild or symptom-free infections that went undiagnosed could lead to symptoms like those of Long Covid. This means the diagnosis of Long Covid shouldn’t only rely on the usual Covid-19 tests, as patients might test negative even if they have Long Covid symptoms.

It’s important to recognize the difficulties faced by people with Long Covid symptoms in getting proper care. Also, including “negative long-haulers” in Long Covid trials and studies is necessary. Understanding and dealing with the widespread impact of Long Covid is very important, even as public attention moves away from the disease.

Challenges in Detecting Long Covid Through Standard Testing

Typical Diagnostic Tests and their Efficacy for Long Covid

To diagnose Long Covid, doctors use three types of tests: blood tests, imaging tests, and pulmonary function tests. These tests help identify the condition and determine its severity. They can reveal indicators of Long Covid, such as T cell or antibody responses to the virus, even if a Covid-19 test is negative. The tests also provide insights into underlying health issues and can inform treatment approaches.

Blood tests detect changes in inflammatory markers, imaging tests identify respiratoryand heart symptoms, and pulmonary function tests assess lung function and cardiovascular health.

Blood Tests

Blood tests are used to diagnose and monitor Long Covid. Healthcare providers may check for T cell or antibody responses to the virus. These indicators can determine if a person has been infected with Covid-19, even if they tested negative.

In a study, 41% of patients with long Covid symptoms had T cell or antibody responses to the virus, despite testing negative. Healthcare providers look for markers of inflammation or specific antibodies related to the virus in blood tests to diagnose Long Covid.

This helps determine if a person’s symptoms are consistent with Long Covid, especially for those who may have had mild or asymptomatic infections and were never officially diagnosed.

Imaging Tests

Imaging tests like chest X-rays, CT scans, and MRI scans are often used to diagnose Long Covid. These tests help healthcare providers find potential lung damage, blood clots, or heart issues related to Long Covid.

It’s important to know that imaging tests may not always definitively show Long Covid, as symptoms can vary widely. Also, while these tests can detect some signs of Long Covid, they have limitations. For example, some patients with Long Covid may have normal imaging results despite significant symptoms.

Additionally, there may be risks from repeated exposure to radiation from certain imaging tests. So, healthcare providers need to consider a mix of imaging tests, patient history, and clinical examination to diagnose Long Covid and provide the best care and support.

Pulmonary Function Tests

Pulmonary function tests measure the volume of air in the lungs, the rate of airflow, and gas exchange. These measurements help in identifying and monitoring respiratory conditions such as asthma, chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis.

Common types of pulmonary function tests include spirometry, which measures the amount of air inhaled and exhaled, and lung diffusion testing, which evaluates how well oxygen and carbon dioxide are transferred between the lungs and the bloodstream.

These tests assist healthcare providers in determining the severity of respiratory conditions, developing treatment plans, and assessing the effectiveness of interventions. For example, spirometry can help diagnose asthma and monitor its progression, while lung diffusion testing can aid in identifying lung diseases affecting gas exchange.

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Potential Indicators of Long Covid on Tests

Blood tests can reveal T cell or antibody responses to the virus, even in cases where the patient tested negative for Covid-19. A study in Neurology found that 41% of patients with long Covid symptoms showed these responses despite having negative test results. This suggests that many cases of long Covid may have gone undiagnosed due to the absence of an official Covid-19 diagnosis.

Imaging tests may not be as effective in detecting potential indicators of long Covid. It is the blood tests that showed promising results in identifying the presence of the virus.

Pulmonary function tests can be used to diagnose potential indicators of long Covid related to respiratory and heart symptoms. These tests can provide valuable diagnostic information about lung and heart function, which are commonly affected in long Covid cases.

Exploring the Intersection of Long Covid with Chronic Fatigue Syndrome

Shared Symptoms and Diagnostic Approaches

Symptoms such as post-exertional malaise, respiratory and heart symptoms, neurological symptoms, and digestive symptoms are commonly reported in both Long Covid and Chronic Fatigue Syndrome. These shared symptoms can make it challenging to differentiate between the two conditions, impacting diagnostic approaches.

Typical diagnostic tests such as blood tests, imaging tests, and pulmonary function tests can help identify potential indicators in diagnosing Long Covid and Chronic Fatigue Syndrome. However, the persistence and reemergence of symptoms over time in Long Covid require a more comprehensive and long-term diagnostic approach compared to standard diagnostic methods for other conditions.

For instance, the study mentioned in Neurology found that 41% of patients with long Covid symptoms had T cell or antibody responses to the virus, despite testing negative. This highlights the need for a more nuanced diagnostic approach that considers the complexity and variability of Long Covid symptoms, providing a more accurate diagnosis for individuals experiencing post-viral syndrome symptoms consistent with Long Covid.

Therapeutic Insights for Long Covid Treatment Derived from Chronic Fatigue Syndrome

Insights from Chronic Fatigue Syndrome can provide valuable guidance in the treatment of Long Covid. Therapeutic approaches that have been effective in treating Chronic Fatigue Syndrome, such as cognitive behavioral therapy and graded exercise therapy, may also benefit individuals with Long Covid.

Similarly, the similarities in symptoms and diagnostic approaches between Chronic Fatigue Syndrome and Long Covid can inform the development of treatment strategies for the latter, offering a basis for understanding and addressing the long-term effects of Covid-19. By drawing on the experiences and findings from Chronic Fatigue Syndrome, healthcare providers can gain valuable insights into the management and treatment of Long Covid, ultimately enhancing the care and support provided to individuals experiencing prolonged symptoms after Covid-19 infection.


1. What tests can detect long Covid?

Tests that can detect long Covid include blood tests to measure specific biomarkers, imaging tests such as chest X-rays or MRIs, and pulmonary function tests to assess lung function.

2. Can blood tests show evidence of long Covid?

Yes, blood tests can show evidence of long Covid by measuring markers such as inflammation levels, organ function, and immune system responses. Examples include checking for elevated levels of C-reactive protein, D-dimer, and cytokines.

3. Are there specific diagnostic tests for long Covid?

Yes, there are specific diagnostic tests for long Covid such as blood tests, imaging tests (like chest X-rays or MRIs), and lung function tests. These tests can help identify ongoing symptoms and determine the best course of treatment.

4. Is there a way to definitively confirm the presence of long Covid through medical tests?

Currently, there is no specific medical test to definitively confirm the presence of long Covid. Diagnosis is based on symptoms and medical history. Testing may be done to rule out other conditions.

5. Can imaging tests such as MRIs or CT scans reveal long Covid symptoms?

No, imaging tests like MRIs or CT scans cannot reveal long Covid symptoms. Symptoms of long Covid are typically diagnosed based on a patient’s reported symptoms and medical history. Tracking oxygen levels and heart rate with devices like pulse oximeters can help manage symptoms.