BREAKING! Study Shows That One Third Of Post-COVID Individuals Who Had Mild Symptoms Have Impaired Lung Function!

Long COVID Research: Alarming study findings from a new research conducted by medical scientist from the Hospital Regional de Alta Especialidad in Mexico has found that almost a third of Post-COVID patients who initially only developed mild symptoms upon infection displayed impaired lung function!


 
To date, only a few studies have assessed lung function in Hispanic subjects recovering from mild COVID-19.
 
Hence the study team examined the prevalence of impaired pulmonary diffusing capacity for carbon monoxide (DLCO) as defined by values below the lower limit of normal (< LLN, < 5th percentile) or less than 80% of predicted in Hispanics recovering from mild COVID-19.
 
The DLCO measures the ability of the lungs to transfer gas from inhaled air to the red blood cells in pulmonary capillaries. The DLCO test is convenient and easy for the patient to perform.
 
The study team also examined the prevalence of a restrictive spirometric pattern as defined by the ratio of forced expiratory volume in 1 s (FEV1) to forced vital capacity (FVC) being ≥ LLN with the FVC being < LLN. Finally, we evaluated previous studies to find factors correlated to impaired DLCO post-COVID-19.
 
For this observational study, adult patients (n = 146) with mild COVID-19 were recruited from a long-term follow-up COVID-19 clinic in Yucatan, Mexico, between March and August 2021. Spirometry, DLCO, and self-reported signs/symptoms were recorded 34 ± 4 days after diagnosis.
 
The Long COVID Research findings showed that at post-evaluation, 20% and 30% of patients recovering from COVID-19 were classified as having a restrictive spirometric pattern and impaired DLCO, respectively; 13% had both.
 
Importantly, the most prevalent reported symptoms were fatigue (73%), a persistent cough (43%), shortness of breath (42%) and a blocked/runny nose (36%).
 
Increased age and a restrictive spirometric pattern increased the probability of having an impaired DLCO while having a blocked nose and excessive sweating decreased the likelihood.
 
Interestingly, the proportion of patients with previous mild COVID-19 and impaired DLCO increased by 13% when the definition of impaired DLCO was < 80% predicted instead of below the LLN. When comparing previous studies, having severe COVID-19 increased the proportion of those with impaired DLCO by 21% compared to those with mild COVID-19.
 
The study findings concluded that about one-third of patients with mild COVID-19 have impaired DLCO thirty-four days post-diagnosis. The period with impaired lung function could even be far longer with most Post-COVID individuals.
 
Also, the study findings showed that one-fifth of patients have a restrictive spirometric pattern.
 
The study findings were published in the peer reviewed journal: BMC Pulmonary Medicine. https://bmcpulmmed.biomedcentral.com/articles/10.1186/s12890-022-02086-9
 < ;br /> The study findings that in the research population, 3 out of 10 patients without pneumonia or reduced SpO2 beyond 90% on room air at sea level (Yucatán, México) have an abnormal lung diffusion during the follow-up.
 
Very little attention has been paid to Post-COVID individuals who initially only had mild symptoms upon SARS-CoV-2 infection.
 
Many of these individuals have lung function abnormalities since mild cases usually develop ground glass opacities instead of lung consolidation. Ground glass opacities are associated with local dysregulations involving endothelial and epithelial injury markers suggesting some degree of venous thromboembolism, endothelial dysfunction, and abnormalities in cardiopulmonary circulatory physiology, which in turn may reflect DLCO abnormalities.
 
In one past meta-analysis research of 12 studies, being female, altered chest computerized tomography, age, higher D-dimer levels, and urea nitrogen were identified as factors for impaired DLCO.
https://pubmed.ncbi.nlm.nih.gov/35663303/
 
The findings of this new Mexican study demonstrated similar odds ratios for age as the meta-analysis study; however, unlike the meta-analysis, sex was not a predictor of impaired DLCO in this study. Furthermore, the meta-analysis did not report that blocked / runny noses or excessive sweating were negative predictors. The results demonstrating that excessive sweating and runny noses were protective against impaired gas exchange are unique and puzzling and could be spurious outcomes.
 
From the data presented, the proportion of those with a runny nose and abnormal sweating was statistically significant between those with impaired DLCO compared to those with normal DLCO. However, when the Benjamini–Hochberg procedure was used to control the false-discovery rate for 25 paired comparisons, these two variables became non-significant.
 
The study team also wanted to determine the variables that predict the percentage of previously infected SARS-CoV-2 patients who had a DLCO impairment during follow-up.
 
Patients with previous severe COVID-19 disease at diagnosis would increase the likelihood of impaired DLCO by nearly 21% compared to those with previous mild COVID-19 disease. When studies used the usual cut-off < 80% of predicted to define DLCO impairment, then 13% more patients would be classified as having an abnormal gas exchange compared to if DLCO impairment was defined as below the LLN. Thus, if using the stricter definition of DLCO impairment as being below the LLN (i.e., below the 5th percentile) for height, age, sex, and ethnicity, 13% fewer patients would be classified as having a reduced DLCO.
 
Hence, the definition of a low DLCO being < 80% of predicted is not correct and may misclassify patients, as the per cent of the predicted value at the LLN (5th percentile) decreases beginning at about 40 years of age.
 
 The study team was not able to measure total lung capacity (TLC) using a body plethysmograph to verify lung restriction; thus, a restrictive spirometric pattern (FEV1/FVC ≥ LLN and FVC < LLN, pre-bronchodilator) was used instead as a surrogate of true lung restriction.
 
It should be noted that the sensitivity to identify true pulmonary restriction (TLC < LLN) with a restrictive spirometric pattern is about 34%, but the specificity is nearly 98%.
 
The negative predictive value (NPV) means that the percentage of patients who do not have a restrictive spirometric pattern and do not have restrictive lung disease is 97%.
 
However, the prevalence of a restrictive spirometric pattern (FEV1/FVC ≥ LLN and FVC < LLN, pre-bronchodilator) in populations is about 3 to 9%.
 
Interestingly, in this group of patients with mild COVID-19, the study team found the restrictive spirometric pattern to be about 20% which is more than double the population average.
 
It should be noted that among persistent symptoms, fatigue and shortness of breath on effort are the most prevalent descriptors included in Long COVID-19, and these were not different in ambulatory patients recovering from mild COVID-19. https://pubmed.ncbi.nlm.nih.gov/34373540/
 
In this new Mexican study, about 74% of the patients experienced undue fatigue, and nearly half experienced shortness of breath on effort and/or a significant cough.
 
The study team concluded, “Nearly one-third of patients with mild COVID-19 have impaired DLCO 34 days post-diagnosis, and one-fifth of patients have lung restriction. The odds of having an impaired DLCO at follow-up increased by 10% for every one-year increase in age (from 25 to 83) and increased 12-fold if a restrictive spirometric pattern was evident. However, having excessive night sweats and a blocked/runny nose each reduced the probability of an impaired DLCO at follow-up by about 90%, demonstrating a protective effect against an impaired gas exchange. In a summary of 22 studies, having severe COVID-19 disease at diagnosis increased the percentage of those with impaired DLCO by 21%. And, if the study used < 80% of predicted to define DLCO impairment, then 13% more patients would be classified as having a poor gas exchange.”
 
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