The persistence of [ME/CFS] after SARS-CoV-2 infection: A systematic review and meta-analysis, 2024, Dehlia et al

The correspondence is from Nuno Sepúlveda and Francisco Westermeier.
The criticisms seem fair. Excerpt:

We then re-assessed the 13 studies selected by the PASC-ME/CFS study for the meta- analysis stage but now under the scope of the EUROMENE research protocol (Table 1). We found that all of these studies satisfied at least one of the exclusion conditions of that protocol: no primary care or community data (n=9); biased samples (n=12); unclear information on ME/CFS case definition (n=1); no application of an ME/CFS case definition (n=1); and studies with overlapping data (n=3). The most important implication is that the pooled prevalence estimates of around 50% reported by the PASC-ME/CFS study can be simply explained by high biased data from PASC cases recruited from PASC support groups who probably had more symptoms, biased data from PASC patients who were already suspected to comply with a ME/CFS diagnosis, and duplicated data.

Our final remark is related to the search query of the PASC-ME/CFS study, which did not account for CFS/ME as an alternative acronym for the disease name. That might explain the exclusion of the study of Simani et al8 from the meta-analysis when it seems to satisfy the inclusion criteria of the PASC-ME/CFS study. This alternative acronym was specified in the query included in the EUROMENE search strategy.

In conclusion, the prevalence reported in the PASC-ME/CFS study is likely to be an overestimation due to biased samples towards suspected ME/CFS cases and data duplication. It might also be based on incomplete data due to a limited search strategy. As a consequence, the prevalence of ME/CFS among the PASC population remains an important open ques- tion, best answered through population studies that prioritize random sampling from the community and primary care settings. We recognize that conducting these studies can be challenging, particularly due to variability in healthcare resources and the complexity of di- agnosing ME/CFS without an objective biomarker. This challenge is illustrated by the scar- city of high-quality epidemiological studies of the disease 6,9.

Notwithstanding this challenge, future research would benefit from adhering to standardized protocols to improve consistency and comparability of findings. In fact, the publication of the EUROMENE protocol was exactly with the purpose of providing a high-quality research template for researcher community. More importantly, an accurate prevalence estimate of the disease is critical to inform healthcare interventions, allocate resources, and develop specialized programs for patients, many of whom face challenges accessing appropriate care. Such a crucial epidemiological information is also critical to raise awareness of the condition within the medical community, reduce stigma, and attract investment in much-needed treatment research.