**3. Results**

Initially, a total of 5412 articles were identified through database searches through MEDLINE and PsycInfo. After examining the titles and available abstracts of articles, and removing duplicate articles, 140 articles remained. The full texts of the 140 articles were examined and evaluated based on article type and content relevance, and distilled down to 33 articles. The articles were further evaluated based on the eligibility criteria, and 21 articles were selected for the final analysis.

The included long COVID studies are shown in Table 1. The chart further specifies the number of patients included in the studies, patient populations, location, median time at the time of symptom assessment, methodology of assessment, key findings, and other additional findings. The studies are ranked in the chart in descending order according to the number of patients included. As noted in the methods section, the heterogeneity of study methods meant the impracticality of quantitative analysis of the studies; the studies are ranked in this order for the purpose of clarity and qualitative interpretations of the studies. When applicable, the percentage of study patients experiencing long COVID symptoms was provided with the key findings of each study.




The long COVID symptoms described by each study were mapped onto a comparison chart between ME/CFS symptoms, matching long COVID symptoms, and unmatched long COVID symptoms, as seen in Table 2. All except four ME/CFS symptoms (motor disturbance, tinnitus/double vision, lymph node pain/tenderness, sensitivity to chemicals, foods, medications, odors) were reported by at least one selected study on long COVID symptoms. All three major criteria symptoms as specified by most ME/CFS case definitions (fatigue, reduced daily activity, post-exertional malaise) were reported by multiple selected long COVID studies, with fatigue being the most reported symptom (13 out of 21 eligible studies). All sub-categories within the minor criteria of ME/CFS (neurologic/pain, neurocognitive/psychiatric, etc.) were matched with long-COVID studies. Only three selected studies met the ≥6 months duration criteria for ME/CFS. There were a few reported long COVID symptoms that were unique from ME/CFS symptoms, including olfactory dysfunction, gustatory dysfunction, and rash.

**Table 2.** Comparison of compiled ME/CFS symptoms to reported long COVID symptoms.


