Introduction

Coronavirus disease 2019 (COVID-19) is caused by a novel coronavirus, known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV2). It has generated huge concern for the high mortality rate and the lack of specific and effective treatment. In India, total number of reported cases are around 4 crores with mortality of 1.19% while cases reported across Himachal Pradesh are 3 lakh with death ratio of 1.35%.^1,2

The survivors of COVID-19 continue to battle the symptoms of the illness, long after they have been clinically tested negative for the disease known as long haulers. The most challenging part of this pandemic is how to manage this COVID-19 sequelae varying from mild fatigue and body aches to severe forms requiring long term oxygen therapy and lung transplantation due to lung fibrosis, significant cardiac abnormalities and stroke leading to impairment in quality of health and life. The most critically ill patients in the context of SARS-CoV-2 infection, develop acute respiratory distress syndrome (ARDS).³ Radiologically, most patients present with bilateral ground glass opacities with or without consolidation, with preference of lower lobes. Pulmonary fibrosis can be idiopathic and considered as age related fibroproliferative disease but chronic inflammation may also be involved in the pathogenesis of lung fibrosis.⁴

Pulmonary fibrosis is also a known sequela of severe and/or persistent damage to lung.⁵ Fibrosis could be viewed as a consequence of a disordered wound healing process and may be directly related to the severity of an inciting event.⁶ Various mechanisms of lung injury in COVID-19 have been described, with both viral and immune mediated mechanisms being implicated.⁷

Lung fibrosis is considered to be due to the abnormal healing of the injured lung parenchyma. In COVID-19 patients, possible sources of injury include cytokine storm due to improper inflammatory response, bacterial co-infections, and thromboembolic events causing microvascular damage and endothelial dysfunction. The renin-angiotensin system is also believed to be involved due to the high affinity of SARS-CoV-2 viral spike protein to the angiotensin-converting enzyme-2 (ACE2) receptor.⁸

Since there are large number of COVID-19 positive patients with pulmonary involvement on CT scans in the setting, the outcome of study about pulmonary fibrosis, inflammatory markers and relation of dose and duration of steroids could possibly help in prognosticating COVID-19 positive patients and help in risk differentiation of patients.

Aims and Objectives

Primary Objective

To evaluate the pulmonary fibrosis cases secondary to Covid-19 pneumonia and its relation with inflammatory markers in patients presenting at Indira Gandhi Medical College, Shimla

Secondary Objectives

To describe the relation of inflammatory markers with pulmonary fibrosis

To describe the relation of dose and duration of steroids with pulmonary fibrosis

Materials and Methods

This was a Prospective Cohort study and included RT-PCR confirmed COVID-19 pneumonia patients reporting to department of medicine, IGMC Shimla (H.P.)

Inclusion Criteria

Patients (>18 years old) with COVID-19 pneumonia confirmed by RT-PCR who were discharged from hospital with any CTSS score (Total score= 25) at presentation were included. The radiological and biochemical characteristics of all patients were collected and analyzed. Imaging features and distributions were analyzed across different time points. Eligible patients were followed up at three months and six months after hospital discharge. Informed written consent was obtained from every participant. In the current study we analyzed all participants who had attended the three month and six month follow up visit.

Exclusion Criteria

Patients who did not give consent to the trial and had underlying ILD, COPD and fibrosis were excluded.

Study Period: One Year- 1^st August 2021 – 31^st July 2022

Data Collection: Participants who completed the follow up and imaging up to six months were included in the study. Demographic characteristics like age, gender, preexisting health condition (Hypertension, DM, CKD, CLD, COPD, Malignancy, Immunosuppression) and smoking history were documented.

Clinical characteristics including main symptoms and signs at admission were recorded. Laboratory indices including TLC count, neutrophil lymphocyte ratio, c reactive protein, ferritin, d-dimer and lactate dehydrogenase were collected at admission and at three and six months respectively. HRCT chest at admission and follow up of three and six months respectively, was done. Important management and therapeutic data including dose and duration of steroid therapy received during hospital stay was recorded. Data regarding use of antifibrotic drugs was also collected.

Statistical Analysis: Data collected was entered into the excel sheet for further processing and statistical analysis. Continuous variables were expressed as mean values and standard deviations while categorical variables were presented as proportions, percentages and 95 % confidence interval. The patients were stratified into two groups according to their CT- SS: Those with CT-SS of 1-17 were considered mild whereas those with CT-SS of 18-25 were considered severe. To find out association between different variables appropriate parametric and non-parametric test of significance was applied depending on type and normality of data. For association p value less than 0.05 were considered as statistically significant. It was done using Epi info version 7.

Results and Observations

Initially we recruited 65 patients (>18 years old) with COVID-19 Pneumonia confirmed by RT-PCR with any CTSS on HRCT chest at presentation. Out of 65 patients, 15 patients were lost to follow up at three months, 5 patients died, and 5 patients were lost to follow up at six months. Eventually, the data of 40 patients of COVID-19 Pneumonia with follow up CT chest at 6 months was recorded and analyzed. None of the patients we studied received antifibrotic agents. The radiological and biochemical characteristics were collected, and results are as follows.

Figure 1: Age and Distribution of study subjects.

Majority of patients 14(35.00%) belonged to age group 51-60 years followed by 30-40 years [8(20.00%)] and 61-70 years [8(20.00%)]. Mean value of age(years) of study subjects was 55.9 ± 13.7 with median (25th-75th percentile) of 57.5(46.5-63.25). Majority of patients 26(65.00%) were males followed by females 14(35.00%)

In majority [37(92.50%)] of patients, presenting symptom was dry cough followed by fever [35(87.50%)], shortness of breath [26(65.00%)], myalgia [7(17.50%)], loss of taste and smell [4(10.00%)], diarrhea [4(10.00%)] and congestion or running nose [1(2.50%)] In majority of In majority [24(60.00%)] of patients, reduced breath sounds was observed. Crepts were present in only 5 out of 40 patients (12.50%) patients, cyanosis [10(25.00%)] was present followed by pallor [2(5.00%)] and icterus [1(2.50%)] Mean value of systolic blood pressure(mmHg), diastolic blood pressure(mmHg), pulse rate (per minute), respiratory rate (per minute) and SpO2 (at room air) of study subjects was 126.35 ± 14.26, 77.45 ± 8, 86.52 ± 13.92, 29.1 ± 5.9 and 80.72 ± 13.15 respectively.

Figure 2: -Distribution of fibrosis of study subjects.

In 15(37.50%) patients, fibrosis was present at 3 months and at 6 months; fibrosis was present in 11 (27.50%) patients.

In our study, 32(80%) out of 40 patients had mild CTSS while 8(20%) patients had severe CTSS at presentation

The proportion of patients with fibrosis at 3 months was significantly lower in mild as compared to severe. (21.88% vs 100% respectively), which was found to be statistically significant (p value <0.0001) Proportion of patients with fibrosis at 6 months was significantly lower in mild as compared to severe (12.5% vs 87.5% respectively) which was found to be statistically significant (p value <0.0001).

Fibrosis was present in majority of patients at three months with deranged TLC, QCRP, NLR, LDH and D-dimer and ferritin, which was found to be statistically significant (p value=0.02 and 0.03 respectively). Fibrosis was present in majority of patients at six months with deranged QCRP, NLR, LDH, D-dimer and also ferritin, which was found to be statistically significant (p value=0.02). On comparing the presence of fibrosis at 3 and 6 months with dose and duration of steroids given during the admission, we found that fibrosis was absent in majority of patients (80%) when the dose of dexamethasone was 6 mg per day as compared to a higher dose (12 mg per day), where only 4% patients did not develop fibrosis (p value <0.00001). Fibrosis at 3 and 6 months was absent when steroids were given for a duration of 6.7 days and 7 days respectively when compared to longer duration of steroids (9.9 days and 10.3 days respectively) (p value = 0.0047 and 0.009 respectively)

Discussion

HRCT played an important role in diagnosis and assessment of disease severity. Among the various COVID-19 pulmonary sequelae, pulmonary fibrosis, which develops due to abnormal healing of injured lung parenchyma⁹, is one of the key concerns as it decreases quality of life. Experiences with SARS and MERS showed that follow up CT is advised in patient recovering from COVID-19 to find out which group of patients is more likely to develop pulmonary fibrosis. Zou and colleagues showed that 30 and 90 day follow up of PCPF patients confirmed that pulmonary fibrosis in some patients will resolve over time; however in majority of patients, it will not resolve¹⁰. Much research has been done on pulmonary fibrosis. However, outcome of fibrosis in post recovery phase and its long-lasting effect on lung parenchyma is still largely unanswered.

This study was conducted in the Medicine department of IGMC Shimla, Himachal Pradesh to describe the outcome of pulmonary involvement in COVID-19 patients, with baseline HRCT chest done, who were discharged after treatment and followed up at 3 and 6 months for fresh or worsening symptoms and radiological changes in HRCT Chest. Then we compared the dose and duration of steroids given at presentation and the inflammatory markers with the radiological changes at three and six months. In our study, based on CT severity scoring at presentation we divided patients into mild (CTSS- 17 or less) and severe group (CTSS-18 or more) and studied the prevalence of fibrosis at three and sixth months in relation to CT severity score at presentation along with inflammatory markers. We also studied the relation of dose and duration of steroids at presentation with pulmonary fibrosis.

Out of the 40 cases we included in our study who completed six months follow up, 26(65%) were males and 14(35%) were females. The male to female ratio was 1.85. This is comparable to a study carried out by Manuel Taboada et al¹¹ in Spain in which 62% patients were males and rest 38% patients were females, the male to female ratio being 1.63. In the study carried out by Xiaoyu Han et al¹². in Wuhan, People’s Republic of China, the male to female ratio was 2.33However, in a study done in Abu Dhabi, UAE by Ghufran et al¹³ in 2021, the males were 85.3%, the females were 14.7% were females, the male to female ratio being 5.66.

The mean age of study population in our study was 55.9+13.7 years. This was similar to study done by Xiaoyu Han et al¹² where mean age of the patients was 54+12 years and it was found that age more than 50 years was an independent predictor for fibrotic like changes in the lung at 6 months. Another study by Chen et al¹⁴ where mean age of the patients was 41.9+13.3 years.

In our study, 32(80%) out of 40 patients had mild CTSS while 8(20%) patients had severe CTSS at presentation (Mean+SD=10.85+5.89). 15(37.5%) out of 40 participants who recovered from COVID-19 pneumonia developed fibrotic like changes in the lung at three months out of which 7(21.8%) patients were in mild group whereas 8(100%) patients were in severe group while at six months, 11(27.5%) patients developed fibrosis; in this group 7 patients (87.5%) were in severe group while 4 patients (12.5%) belonged to mild group. Proportion of patients with fibrosis at 6 months and 3 months was significantly lower in mild as compared to severe group (p value<0.0001).

Similar prospective study was conducted by Xiaoyu Han et al¹² where pulmonary sequelae of COVID-19 patients was assessed and follow up HRCT chest were done at 17+ 11 days and 175+ 20 days in which CT severity score of patients was calculated. 40 of the 114 participants (35%) develop fibrotic like changes; in this group, most of the fibrotic like changes (22 of 40- 55%) manifested at 6 month follow up whereas 74(65%) showed either complete radiologic resolution or residual ground glass opacification. Similar to our study higher CT score (>18) on initial CT scan was independent predictor of development of fibrotic like changes in the lung after 6 months follow up. The laboratory results also showed higher d dimer and c reactive protein levels in patients with fibrotic like changes while in our study, fibrosis was present in majority of patients at three months with deranged TLC, QCRP, NLR, LDH (40%, 38.24%, 42.86% and 42.42% respectively) and also D-dimer and ferritin (60% and 46.67% respectively), which was found to be statistically significant(p value=0.02 and 0.03 respectively) and fibrosis was also present in majority of patients at six months with deranged QCRP, NLR, LDH, D-dimer (29.9%, 31.43%, 33.3% and 40% respectively) and also ferritin (36.67%), which was found to be statistically significant (p value=0.02) The difference in outcome of our study and the above-mentioned study was primarily due to small sample size. Also, the extent of fibrosis was not quantified in both the studies.

Another study was conducted by Rabab Yasin et al¹⁵ in Egypt including 210 patients to predict lung fibrosis in Post COVID-19 patients. At least one follow up chest CT was done at 20-65 days after discharge and it showed fibrosis in 48.1% patients while 51.9% had no residual fibrosis with majority of patients with fibrosis in older age group, comparable to our study. The patients with fibrosis also had higher rate of ICU admissions, the factor which was not included in our study. They also reported higher level of inflammatory markers- c-reactive protein, d-dimer, ferritin in patients with fibrosis similar to our study suggesting that deranged inflammatory markers are more associated with pulmonary fibrosis. Patients (83.8%) were given pulse steroid therapy in contrast to our study where dose and duration of steroid therapy was also evaluated in relation to fibrosis.

We described outcome of COVID-19 based on presence or absence of fibrosis at 6 months and found out that fibrosis was absent in majority of patients when dose of dexamethasone given was 6 mg (80%) compared to 12 mg (4%) (p value <0.00001). Also, we found that the mean duration of steroids 6.7+3.94 days and 7+3.8 days was associated with absent fibrosis at three and six months respectively, which was statistically significant (p value=0.0047 and 0.009 respectively). Contrary to our study, Manuel Taboada et al¹¹ conducted a study where 200 patients were assigned in 1:1 ratio to receive low dose (6 mg) once daily for 10 days and high dose (20mg) once daily for five days followed by 10 mg for additional 5 days. They found that high dose of dexamethasone reduced clinical worsening within 11 days after randomization, compared with low dose. Different sample size and duration of steroids in the above-mentioned studies was the main difference in the outcome of these two studies.

Limitations

Firstly, sample size was very small and follow up was done for only 6 months. Patients with fibrotic like changes require longer follow up to determine whether these changes are permanent or reversible. Only semi quantitative scores in the form of CT severity score was used which was shown to be correlated with the degree of pulmonary fibrosis. The extent of fibrosis was not quantified. Lack of histologic correlation is also a limitation. Therefore, further studies are needed to find whether fibrotic like changes on CT scans represent true pathologic fibrosis.

Therefore, identifying the predictive factors for pulmonary fibrosis such as higher CTSS in initial HRCT chest, raised inflammatory markers at presentation and high dose of steroid (12mg dexamethasone) for a longer duration in clinical practice can help in preventing the development and progression of lung fibrosis.

Conclusion

In conclusion, most of the patients with mild lung involvement (CTSS-17 or less) at presentation, fibrosis was significantly lower at 3 months and 6 months of follow up in comparison to patients with severe lung involvement (CTSS>17). At 3 months fibrosis was present in majority of patients with deranged TLC, QCRP, NLR, LDH and also D-dimer and ferritin which was found to be statistically significant. At 6 months fibrosis was present in majority of patients with deranged QCRP, NLR, LDH, D-dimer along with ferritin which was significant. Our study also suggested that steroids for an average duration of 10 days at presentation was significantly associated with improvement in fibrosis.

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