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Original Clinical Science—General

COVID-19 Outcomes Among Solid Organ Transplant Recipients: A Case-control Study

Sharma, Pratima MD, MS1; Chen, Vincent MD, MS1; Fung, Christopher M. MD2; Troost, Jonathan P. PhD3; Patel, Vaiibhav N. MD1; Combs, Michael MD1; Norman, Silas MD1; Garg, Puneet MD1; Colvin, Monica MD1; Aaronson, Keith MD, MS1; Sonnenday, Christopher J. MD, MHS4; Golob, Jonathan L. MD, PhD1; Somers, Emily C. PhD, ScM1,5; Doshi, Mona M. MD1

Author Information
doi: 10.1097/TP.0000000000003447

Abstract

INTRODUCTION

Severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) that causes the clinical syndrome known as COVID-19 is a public health emergency and was declared a pandemic in March 2020.1 COVID-19 is highly contagious and the clinical presentation ranges from asymptomatic carriers to severe disease resulting in respiratory failure, shock, and multiorgan failure. As of June 17, 2019, there are 8.4 million confirmed cases and 452 067 deaths worldwide, of which one-fourth of the cases and deaths occurred in the United States with a case fatality rate of 5.8%.2 New York City was the first epicenter for COVID-19 in the United States followed by the Detroit metro and surrounding counties in Michigan. During the early phase of COVID-19 pandemic, there were significant decreases in total waitlist additions and transplant surgeries with increases in waitlist deaths in the majority of the US transplant domains. This impact was more prevalent in areas with high burden of COVID-19, for example, New York City.3

Solid organ transplant (SOT) recipients are potentially at a higher risk of contracting or developing severe COVID-19 due to underlying immunosuppression, frequent contact with healthcare providers, and high prevalence of comorbidities such as obesity, hypertension, diabetes, chronic kidney disease, and heart disease, which are known risk factors for severe disease related to COVID-19.4-6 Given the strong pathophysiological role of cytokine storm in many of the manifestations of severe disease in COVID-19, it is possible that SOT recipients with COVID-19 may not mount as severe as an inflammatory response because of immunosuppression, which may be protective against severe disease.7,8 To date, the studies describing the clinical course of COVID-19 among SOT recipients, risk factors, and outcomes have been case series or case reports.4,6,9-11 In this study, we characterized COVID-19 illness and its clinical course among SOT recipients. Furthermore, we compared the outcomes between SOT recipients with COVID-19 and matched non-SOT controls with COVID-19 using a case-control study design.

METHODS AND MATERIALS

Study Population and Data

Within the Michigan Institute for Clinical and Health Research, we developed a COVID-19 Rapid Response Registry for clinical characterization of persons with SARS-CoV-2 infection. The Registry includes core items from the International Severe Acute Respiratory and Emerging Infection Consortium Clinical Characterization Protocol.12

This study was performed as a case-control study. The cases consisted of all adult SOT recipients diagnosed with COVID-19, based on a positive confirmatory test for SARS-CoV-2 by reverse transcriptase polymerase chain reaction (PCR), between March 10, 2020 to May 15, 2020. Controls were likewise adult patients diagnosed with COVID-19 diagnosis using PCR, but no history of being an SOT recipient or candidate and sought care at Michigan Medicine during the study period. Up to 3 controls were individually matched from a cohort of 680 COVID-19 patients to each case based on age (±5 y), race (White, Black, or Others), and admission status (admitted to the hospital or treated as outpatient) to circumvent the selection bias. Our small SOT sample size restricted the use of propensity matching or the number of variables we could match on, and because differences cannot be explored for matching variables since by definition the distributions are similar. Moreover, matching on comorbidities will not allow to examine the association between COVID-19 and comorbidities. We selected age and race with the intent that they would also balance comorbidities. SOT recipients with COVID-19 were matched on admission status around the same time to account for the evolving management during the early phase of pandemic. Patients were followed up until death or June 10, 2020. This study was approved by the University of Michigan Institutional Review Board and completed in accordance with the Declaration of Helsinki.

Demographics, laboratory results, treatment information, and outcomes were abstracted from the medical chart, and data integrity of electronic health record was cross-checked by manual review of the medical records. Comorbidities were ascertained from documentation at the time of admission or from the last clinic note. Baseline renal function was assessed via estimated glomerular filtration rate using the Chronic Kidney Disease Epidemiology Collaboration formula based on serum creatinine at the time of admission or the last available serum creatinine before admission.13 Patients were classified into stages of chronic kidney disease (CKD) as per Kidney Disease Improving Global Outcomes guidelines.14 Most patients admitted to the hospital with COVID-19 had baseline and serial assessment of markers of inflammation including high-sensitivity C-reactive protein, serum ferritin, procalcitonin, lactate dehydrogenase, d-dimers, and high-sensitivity troponin.

Our institution has a live document that provides the written guidance for COVID-19 management. The criteria for intubation and transfer to ICU remained the same throughout the study independent of SOT status. An infectious diseases consult was recommended before the initiation of medical therapy for COVID-19 illness. Initially per local guidance, hydroxychloroquine (HCQ) was used with or without azithromycin for patients with COVID-19 who required supplemental oxygen. The dosing regimen was 600 mg twice a day on day 1, followed by 200 mg twice a day for 5 d. The local use of HCQ was abandoned by April 4, 2020 because of data suggesting lack of benefit, although regional hospitals continued to use HCQ.15 Baseline electrocardiogram was taken on all the patients who were started on treatment with HCQ.

Tocilizumab was considered for COVID-19 in patients with rapid respiratory deterioration and evidence of hyperinflammation (described in more detail elsewhere),16 and when enrollment into a randomized controlled trial of IL-6 inhibition was not an option.

Outcomes

The primary outcome was death and the secondary outcomes were severe disease defined as transfer to the intensive care unit and requiring at least humidified high flow oxygen, need for intubation and use of renal replacement therapy (RRT) during hospitalization. Criteria for intubation and starting RRT were determined by the intensivist and nephrology consultation team.

Statistical Analyses

The continuous variables were expressed as median and interquartile range (IQR), and the categorical variables were expressed as counts and percentage. We used the Kruskall–Wallis and chi-square or Fisher exact tests to compare continuous and categorical variables between cases and controls.

We used the Kaplan–Meier survival analysis to examine the cumulative probability of death among cases and controls. We used Cox regression analysis to assess the factors associated with the risk of death. We fitted 3 models and adjusted for the covariates: (1) SOT status (cases versus controls); (2) severe disease and SOT status; and (3) sex and comorbidities [CKD, hypertension, diabetes, chronic obstructive pulmonary disease (COPD) and cardiovascular disease (CVD)]. The rationale behind choosing sex, CKD, and COPD was based on the following observation(s): (1) significantly higher proportion of males than females in the SOT group (Table 1); (2) significantly higher prevalence of CKD and hypertension in SOT compared with the non-SOT group (Tables 2 and 3) significant association of diabetes, COPD and CVD with death in univariate analysis (Table S1, SDC, http://links.lww.com/TP/C9).

TABLE 1. - Comparison of baseline characteristics and peak inflammatory markers between cases and controls
Characteristic CasesMedian (IQR) or n (%) ControlsMedian (IQR) or n (%) P
Demographics
 Age (y), median (IQR) 60.0 (54.0–69.0) 60.0 (52.0–67.0) 0.67
 Female, n (%) 7 (17) 61 (50.4%) <0.001
 Males, n (%) 34 (83%) 60 (49.6%)
 Race, n (%) 0.72
  Black, n (%) 27 (66) 81 (67)
  White, n (%) 13 (32) 39 (32)
  Unknown, n (%) 1 (2) 1 (1)
 Admitted, n (%) 35 (85) 104 (86) 0.93
Comorbidities
 BMI, median (IQR) (n = 157) 27.0 (24.2–32.1) (n = 41) 31.7 (26.7–38.0) (n = 116) <0.001
  Underweight, n (%) 3 (7) 2 (2)
  Healthy weight, n (%) 14 (34) 16 (14)
  Overweight, n (%) 10 (24) 28 (24)
  Obese, n (%) 14 (34) 70 (60)
 Heart disease, n (%) 14 (34) 31 (26) 0.29
 CKD, n (%) 33 (80) 36 (30) <0.001
 Obstructive sleep apnea, n (%) 8 (20) 29 (24) 0.56
 Cerebrovascular disease, n (%) 6 (15) 12 (10) 0.41
 Dementia, n (%) 2 (5) 8 (7) 0.69
 Diabetes, n (%) 23 (56) 55 (45) 0.24
 Liver disease, n (%) 7 (17) 11 (9) 0.16
 Malignancy, n (%) 7 (17) 14 (12) 0.36
 HTN, n (%) 39 (95) 73 (60) <0.001
 CKD stage, n (%) (n = 155) <0.001
  eGFR >60 mL/min/m2 8 (20) 83 (75)
  eGFR 30–60 mL/min/m2 23 (56) 20 (18)
  eGFR <30 mL/min/m2 10 (24) 8 (7)
  Missing, n 0 10
 COPD, n (%) 5 (12) 19 (16) 0.58
 Asthma, n (%) 2 (5) 12 (10) 0.32
 AIDS, n (%) 0 (0) 3 (2) 0.31
Baseline laboratory values
 Absolute lymphocyte count (n = 144) 0.9 (0.6–1.2) (n = 28) 1.0 (0.7–1.5) (n = 116) 0.22
 Absolute neutrophil count (n = 144) 4.9 (2.9–7.3) (n = 28) 4.7 (3.3–7.1) (n = 116) 0.57
 HGB, median (IQR) (n = 145) 11.5 (9.6–13.0) (n = 28) 13.0 (11.5–14.0) (n = 117) 0.01
 Lymphocyte (n = 144) 12.7 (7.6–16.4) (n = 28) 16.4 (10.0–21.3) (n = 116) 0.03
 Neutrophils (n = 144) 78.8 (63.5–83.7) (n = 28) 75.5 (68.0–80.2) (n = 116) 0.38
 Platelets (n = 145) 152 (106.5–205.5) (n = 28) 207 (155.0–263.0) (n = 117) <0.001
 WBC (n = 145) 6.8 (5.4–9.4) (n = 28) 6.3 (4.8–8.7) (n = 117) 0.46
 Albumin (n = 142) 3.8 (3.3–4.2) (n = 32) 3.9 (3.6–4.3) (n = 110) 0.05
 Alkaline phosphate (n = 142) 79.0 (53.0–108.0) (n = 33) 76.0 (63.0–104.0) (n = 109) 0.69
 ALT (n = 141) 26.0 (20.0–39.0) (n = 33) 33.0 (22.5–51.5) (n = 108) 0.13
 AST (n = 142) 37.0 (27.0–69.0) (n = 33) 41.0 (29.0–65.0) (n = 109) 0.37
 Total bilirubin (n = 141) 0.6 (0.4–0.8) (n = 32) 0.5 (0.4–0.8) (n = 109) 0.53
 BUN (n = 145) 40.0 (28.5–64.5) (n = 28) 17.0 (12.0–26.0) (n = 117) <0.001
 CO2 (n = 145) 20.5 (18.0–25.5) (n = 28) 26.0 (23.0–28.0) (n = 117) <0.001
 CR (n = 146) 2.1 (1.6–4.2) (n = 29) 1.0 (0.8–1.4) (n = 117) <0.001
 TBILI (n = 141) 0.6 (0.4–0.8) (n = 32) 0.5 (0.4–0.8) (n = 109) 0.53
 CRP (n = 132) 9.6 (5.1–21.8) (n = 29) 7.4 (4.5–15.6) (n = 103) 0.20
 D-dimer (n = 120) 1.7 (1.0–4.2) (n = 24) 1.2 (0.6–2.0) (n = 96) 0.03
 FERRITIN (n = 135) 1330 (931–1850) (n = 30) 617 (224–1370) (n = 105) 0.001
 IL-6 (n = 28) 78.3 (44.1–507.6) (n = 4) 38.5 (21.8–91.9) (n = 24) 0.39
 LDH (n = 131) 307 (230–564) (n = 32) 390 (271–500) (n = 99) 0.32
Peak inflammatory markers
 Peak serum ferritin (n = 145) 1531 (1100–2776) (n = 27) 798 (281–1580) (n = 105) 0.002
 Peak d-dimer (n = 132) 2.5 (1.7–7.4) (n = 25) 1.5 (1.0–4.9) (n = 97) 0.04
 Peak CRP (n = 134) 18.5 (5.0–30.7) (n = 30) 10.8 (5.8–19.1) (n = 104) 0.21
 Peak LDH (n = 126) 488 (234–627) (n = 27) 420 (321–595) (n = 99) 0.98
 Peak creatinine (n = 147) 2.8 (2.1–5.9) (n = 30) 1.1 (0.9–1.7) (n = 117) <0.001
 Peak procalcitonin (n = 126) 1.8 (0.5–16.1) (n = 26) 0.2 (0.1–1.2) (n = 100) <0.001
 Peak hs troponin (n = 111) 63.0 (32.0–203.0) (n = 21) 18.5 (10.0–46.0) (n = 90) <0.001
 Peak SOFA (n = 127) 7.5 (4.5–13.5) (n = 24) 4.0 (3.0–7.0) (n = 103) 0.01
Treatment
 HCQ treatment, n (%) 12 (29) 34 (28) 0.89
 IL-6 inhibitors, n (%) 11 (27) 11 (9) 0.01
 Pressors, n (%) 6 (17) 8 (8) 0.15
ALT, alanine aminotransferase; AST, aspartate aminotransferase; BMI, body mass index; BUN, blood urea nitroge; CI, confidence interval; CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disease; CR, creatinine; CRP, c-reactive protein; eGFR, estimated glomerular filtration rate; HCQ, hydroxychloroquine; HGB; HR, hazard ratio; HTN, hypertension; IQR, interquartile range; LDH, lactate dehydrogenase; SOT, solid organ transplant; TBILI, total bilirubin; WBC, white blood cells.

TABLE 2. - Time to death: results of Cox PH models (20 deaths; 6 among SOT cases, 14 among controls)
HR [95% CI] P
Model 1: unadjusted
 Case vs control 1.11 [0.43, 2.89] 0.83
Model 2: severe disease adjusted
Case vs control 0.84 [0.32, 2.20] 0.73
Severe disease (yes vs no) 8.41 [2.80, 25.30] <0.001
Model 3: sex and comorbidity adjusted
 Case vs control 0.90 [0.31, 2.63] 0.84
 Female vs male 0.75 [0.25, 2.24] 0.61
 CKD (yes vs no) 1.85 [0.54, 6.40] 0.33
 COPD (yes vs no) 2.80 [1.09, 7.21] 0.03
 HTN (yes vs no) 0.34 [0.07, 1.55] 0.16
 DM (yes vs no) 2.94 [0.92, 9.39] 0.07
 CVD (yes vs no) 3.14 [1.09, 9.07] 0.03
CI, confidence interval; CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disease; CVD, cardiovascular disease; DM, diabetes mellitus; HR, hazard ratio; HTN, hypertension; RRT, renal replacement therapy; SOT, solid organ transplant.

TABLE 3. - Comparison of outcomes between SOT recipients (cases) and non-SOT (controls) with COVID-19
Model Matched set conditional odds ratio [95% CI] P
Severe diseaseCases (N = 18) vs controls (N = 34)
 Unadjusted 2.01 [0.94, 4.28] 0.07
 Sex, CKD, COPD, HTN, DM, and CVD adjusted 1.94 [0.70, 5.34] 0.20
 Sex, CKD, COPD, HTN, DM, CVD, and ferritin adjusted* 1.46 [0.49, 4.32] 0.50
IntubationCases (N = 11) vs controls (N = 21)
 Unadjusted 1.69 [0.73, 3.91] 0.22
 Sex, CKD, COPD, HTN, DM, and CVD adjusted 1.45 [0.47, 4.50] 0.52
 Sex, CKD, COPD, HTN, DM, CVD, and ferritin adjusteda 1.69 [0.50, 5.72] 0.40
RRT useCases (N = 11) vs controls (N = 7)
Unadjusted 6.94 [2.18, 22.12] 0.001
 Sex, CKD, COPD, HTN, DM, and CVD adjusted 5.08 [0.90, 28.88] 0.07
 Sex, CKD, COPD, HTN, DM, CVD, and ferritin adjusteda 5.01 [0.82, 30.72] 0.08
aSerum ferritin was available in 30 cases and 105 controls.
CI, confidence interval; CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disease; CVD, cardiovascular disease; DM, diabetes mellitus; HR, hazard ratio; HTN, hypertension; RRT, renal replacement therapy; SOT, solid organ transplant.

We used conditional logistic regression analysis to compare the odds of severe disease, intubation, and RRT between cases and controls. The first unadjusted model included age, race, and admission status. The second was adjusted for sex and comorbidities adjusted, and the third model was adjusted for sex, CKD, COPD, and serum ferritin level (at admission). These covariates were significantly different between cases and controls.

In a secondary post hoc analysis, we examined the association between HCQ and survival separately for cases and controls (after observing an association suggesting the excess risk of death among cases but not controls) by testing the interaction of HCQ with SOT status on death using Cox regression. The first unadjusted model showed the interaction between HCQ and SOT status (cases versus control). The second model was inverse probability treatment weighting (IPTW) propensity matched cases and control.17-19 The propensity score of HCQ treatment was based on the presence of heart disease, CKD, diabetes, and chronic pulmonary disease. The third model tested for interaction and severe disease.

Last, we performed sensitivity analyses by excluding the cases and controls who were managed at home for primary and secondary outcomes. All analyses were performed in SAS 9.4.

RESULTS

Patient Characteristics

Forty-one SOT recipients tested positive for SARS-CoV-2 during the study period. The SOT recipients had the following transplants: 9 heart, 3 lung, 16 kidney, 8 liver and 5 dual organ transplant recipients (2 kidney-pancreas transplant, 1 combined heart-kidney, 1 simultaneous liver-kidney, and 1 kidney after liver). Of those 41 SOT recipients, 6 were managed at home and the remaining 35 were admitted to the hospital. The median age of cases was 60 y (IQR: 54–69), and they were predominantly males (80%) and Black (67%) (Table 1). The median time from transplant to COVID-19 infection was 9 y (IQR: 5–16). None of the recipients were within the first year of transplant. The most common symptom was shortness of breath (43%) followed by cough (32%) and fever (32%). Fatigue and myalgia was seen in 27% and 12% and diarrhea in 15% of the cases.

Baseline immunosuppression consisted of calcineurin inhibitor (tacrolimus or cyclosporine) in 36 SOT recipients (88%), with tacrolimus being most common (87%). Twenty-six patients (63%) were on chronic prednisone therapy. The dose of prednisone was 5 mg once a day in all of them. Twenty-two patients (54%) were on mycophenolate. Calcineurin inhibitors and steroids were continued in all the patients where as mycophenolate was held in all but 2 SOT recipients after the COVID-19 diagnosis.

There were 121 non-SOT matched controls with a median age of 60.5 y (IQR: 52–67). In the non-SOT group, 50% were male, and 67% were Black. Sixteen (13%) of 121 were managed at home. Table 1 shows the comparison of baseline characteristics between SOT and non-SOT. While they were well-matched on age, race and admission status, SOT recipients were more likely to be males (83% versus 50%; P < 0.001), to be at a healthy weight (34% versus 14%; P < 0.001), to have CKD stage 3 and higher (80% versus 25%; P < 0.001), and to have hypertension (95% versus 60%; P = 0.004). There was no difference in white blood cell count and absolute lymphocyte count between the 2 groups, but the platelet counts were lower in SOT recipients compared to non-SOT COVID-19 patients (Table 1). There were no differences in the liver chemistries or baseline and peak values of C-reactive protein between the groups. The SOT recipients had higher levels of d-dimer and ferritin on admission compared with non-SOT patients with COVID-19. The peak sequential organ failure assessment score was higher for SOT compared to non-SOT recipients with COVID-19 suggesting higher severity of organ dysfunction among SOT recipients than non-SOT patients with COVID-19 (Table 1).

A third of patients were treated with HCQ for COVID-19, and its use was similar among SOT and non-SOT matched controls with COVID-19. However, a significantly higher proportion of SOT recipients were treated with tocilizumab compared with non-SOT matched controls (27% versus 9%; P = 0.01). These differences were due to lack of eligibility of SOT recipients for placebo controlled clinical trial (eg, remdesivir and sarilumab) and were offset by increased use of tocilizumab. Fourteen patients (2 SOT: 1-sarilimab and 1 convalescent serum; 12 non-SOT: 5 remdesivir, 5 sarilumab, 1 ORCHID, and 1 convalescent serum) were enrolled in various placebo controlled clinical trials for COVID-19 therapy (remdesivir and IL-6 inhibitors). None of the patients received remdesivir for compassionate care.

The overall follow-up time was 51 d (IQR: 23–65). There was no difference in the median follow-up time between cases and controls (SOT recipients: 48 d [IQR: 35–56], non-SOT matched control: 53 d [IQR: 16–66]; P = 0.64).

Primary and Secondary Outcomes

Of 41 cases, 36 were admitted to the hospital and 18 had severe disease, 11 required intubation, 11 required RRT, and 2 required extracorporeal membrane oxygenation (Figure 1). Of 121 controls, 104 were admitted to the hospital and 34 had severe disease, 21 needed intubation, and 7 needed RRT (Figure 2). There was no significant difference in the median length of stay between SOT (8 d [IQR: 5–22]) and non-SOT matched controls (IQR: 6 d [3–14]) with COVID-19. The time spent in the intensive care unit was also similar in both the groups (SOT: 12 d [IQR: 6–16]) and non-SOT matched controls (8 d [IQR: 4–14]).

FIGURE 1.
FIGURE 1.:
Outcomes of solid organ transplant recipients with COVID-19.
FIGURE 2.
FIGURE 2.:
Outcomes of nonsolid organ transplant matched controls with COVID-19.

There were 6 deaths among SOT (3 heart, 2 kidney, and 1 liver) and 14 deaths among non-SOT COVID-19 matched controls, respectively. All but 1 among SOT recipients received HCQ and azithromycin, 1 received hydrocortisone for 7 d and 1 received dexamethasone for COVID-19 treatment. All 6 of them developed multiorgan failure: 2 had myocarditis, 1 developed progressive right heart failure and limb ischemia, and 1 with severe encephalopathy. Bacterial superinfection was present in 3 of the 6 SOT recipients who died during their hospitalization.

Figure 3 shows the similar cumulative survival in both the groups. The overall case fatality rates were similar for SOT (14.6%) and non-SOT (11.4%) COVID-19 patients. For those who were admitted, the case fatality rate was 17% for SOT and 13% for non-SOT matched controls (nonsignificant difference); for those with severe disease, the case fatality rate was 33% for SOT recipients compared with 29% for non-SOT matched controls with COVID-19 (nonsignificant difference). In an unadjusted analysis, age, heart disease, dementia, diabetes, and COPD were associated with increased risk of death in addition to the sequential organ failure assessment score. Lymphocyte count, serum blood urea nitrogen, and baseline serum potassium were also significantly associated with increased risk of death (Table S1, SDC, http://links.lww.com/TP/C9). We also examined the effect of the month of admission and SOT status on death. The month of admission (March versus May: P = 0.58; April versus May: P = 0.08) and SOT status (P = 0.46) were not associated with the hazard of death suggesting that the changes in protocol made during the course of the study period had no impact on outcomes in the overall cohort of patients with COVID-19 in our center.

FIGURE 3.
FIGURE 3.:
Cumulative survival in COVID-19 infected patients stratified by cases and control.

Table 2 shows the various covariate adjusted models. Severe disease was associated with high risk of death independent of SOT recipient status (Table 2). In a separate model adjusted for sex, significantly different comorbidities, and SOT status, COPD and CVD were independently associated with high risk of death independent of SOT status (Table 2). There was a trend toward high mortality risk and diabetes, it did not reach statistical significant.

The odds of severe disease and intubation were similar between the 2 groups (Table 3). The odds of RRT were significantly higher in SOT recipients compared to non-SOT matched controls with COVID-19 in unadjusted analyses (Model 1: SOT versus non-SOT matched upon age, race, and admission status). There was a trend toward high odds of RRT use in comorbidity adjusted and comorbidity and ferritin adjusted models (Table 3). Of the 11 SOT recipients who required RRT (4 kidney, 5 heart, and 1 each were lung and liver), 4 died, 2 were transitioned to chronic dialysis, and 5 had renal recovery. Of the 7 non-SOT matched controls with COVID-19 who required RRT, 3 died, 3 were transitioned to chronic dialysis, and 1 had renal recovery.

Post Hoc Secondary Analysis: Association With HCQ and Death

Treatment of COVID-19 with HCQ was associated with increased risk of death among SOT recipients (hazard ratio [HR] = 13.24, P = 0.02) but not among non-SOT matched controls (HR = 0.59, P = 0.41) (Figure 3). In an unadjusted model examining the interaction between HCQ and SOT status on death, we found a significant interaction where SOT recipients treated with HCQ had a significantly higher hazard of death compared to those who were not treated with HCQ (Table 4), but this relationship was not seen in controls.

TABLE 4. - HCQ treated associated with increased mortality among SOT cases
Model HR [95% CI] P
Model 1: unadjusted interaction (n = 162; n = 20 events)
 HCQ treated vs untreated (SOT) 13.16 [1.54, 112.63] 0.02
 HCQ treated vs untreated (non-SOT) 0.58 [0.16, 2.07] 0.40
Model 2: IPTW interactiona (n = 162; n = 20 events)
 HCQ treated vs untreated (SOT) 9.37 [1.82, 48.10] 0.01
 HCQ treated vs untreated (non-SOT) 0.72 [0.35, 1.49] 0.37
Model 3: severe disease adjusted (n = 162; n = 20 events)
 HCQ treated vs untreated (SOT) 10.62 [1.24, 91.09] 0.03
 HCQ treated vs untreated (non-SOT) 0.44 [0.12, 1.58] 0.21
 Severe disease (yes vs no) 8.54 [2.81, 25.96] <0.001
Results of Cox PH regression models.
Among SOT cases: 5/12 deaths among HCQ treated; 1/29 deaths among untreated.
Among matched controls: 3/34 deaths among HCQ treated; 11/87 among untreated.
aPropensity scores of HCQ treatment based on CAD, CKD, diabetes, and COPD.
CI, confidence interval; CAD, coronary artery disease; CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disease; HCQ, hydroxychloroquine; HR, hazard ratio; IPTW, inverse probability treatment weighting; SOT, solid organ transplant.

In an IPTW propensity matching on heart disease, CKD, diabetes, and COPD (covariates based on differences between cases and control and previous studies), the interaction between SOT recipient status and treatment with HCQ was still significant. This association was not significant for the controls. Figure 4 shows the adjusted survival among cases by HCQ treatment. Similarly, in the model adjusted for interaction term and severe disease, the interaction between HCQ and SOT recipients and severe disease were both significant.

FIGURE 4.
FIGURE 4.:
Survival stratified by hydroxychloroquine uses in cases and controls. A, Covariate adjusted survival among HCQ treated SOT vs HCQ untreated SOT (cases). B, Covariate adjusted survival among HCQ treated SOT vs HCQ untreated SOT (controls). HCQ, hydroxychloroquine; SOT, solid organ transplant.

Sensitivity Analysis

Sensitivity analysis of excluding SOT and non-SOT matched controls who were not admitted to the hospital did not change the results for primary and secondary outcomes.

DISCUSSION

The COVID-19 pandemic has the potential to severely impact SOT recipients, who are extremely vulnerable to infection because of their weakened immune system. This has a driven concern that SOT recipients will both be at increased risk to contract and to develop worse outcomes from COVID-19. Here, we compared the clinical course and outcomes of COVID-19 infection in SOT recipients with age-, race- and admission status–matched non-SOT controls. The case fatality rate was similar between SOT recipients and their matched non-SOT controls with COVID-19 despite high SOFA score among SOT cases. Although the SOT recipients had higher baseline and peak inflammatory response than controls, the odds of COVID-19 associated severe disease and intubation rates were similar in both the groups. However, the use of RRT was significantly higher among cases compared with the controls.

In contrast to early reports of high case fatality rate in SOT reported by transplant centers in NY up to 52.9%, several recent studies including recent study from Detroit20 and a systematic review of 24 studies, with 39 SOT recipients reported lower fatality rate of 23% and 25%, respectively. This is in alignment with our findings of case fatality rate of 17%.4,5 This could be due to differences in the baseline characteristics of SOT recipients such as the median time to COVID-19 from transplant, which was longer in our cohort or the use of emerging COVID-19 treatments in different communities and settings.

While the SOT recipients did not experience higher risk of death, the need for RRT support was significantly higher compared to non-SOT with COVID-19. This can be explained due to increased prevalence CKD stage 3 or higher in SOT versus non-SOT group due to use of CNI and the presence of a solitary kidney in half of SOT recipients. Epidemiological data revealed the severe illness rate of COVID-19 is as high as 25%, and even though the lungs are the main organs affected, the kidney is also often affected in severe illness.9 In a study of 36 kidney transplant patients, the use of RRT was 21%.21 A meta-analysis reported that the presence of CKD increased the odds of COVID-19 disease severity by >2-fold.22 The use of RRT was higher among SOT recipients compared with non-SOT matched controls despite a similar proportion of severe disease in both the groups in our study. CKD is a known comorbidity among SOT recipients.23,24 Moreover, acute kidney injury (AKI) is a common complication of COVID-19. In 1 study of 161 patients with severe COVID-19, AKI was seen in 28% of the patients and 35% of those had stage 3 CKD or higher.25 One may argue that AKI in CKD created a perfect storm for the increased need for RRT in SOT recipients. However, this effect was independent of baseline CKD. Finally, the question arises whether the AKI in COVID-19 is a direct viral effect mediated through angiotensin-converting enzyme-2 in kidney or related to systemic inflammatory response as a result of cytokine storm.

Data reported by the Michigan Department of Health and Human Services demonstrated that Blacks were overrepresented in COVID-19 cases and deaths. Black race represents 15% of the total population in Michigan, yet accounted for 35% of COVID-19 cases and 42% of COVID-19-related deaths. This is in striking contrast to 40% of COVID-19 cases and 26% of COVID-19-related deaths occurring in Whites who represent 75% of population in Michigan. We validated this finding among SOT recipients with COVID-19. Blacks or African Americans constitute 9%–10% of all SOT recipients in our center but accounted for two-thirds of all the SOT COVID-19 cases. Medical comorbidities like hypertension, CKD, CVD, and diabetes associated with poor outcomes in COVID-19 also have a high prevalence among Black race. It is increasingly recognized that health inequities are often rooted in structural racism.26 Furthermore, data released by the city of Detroit showed that COVID-19 cases and deaths are not equally distributed by ZIP code.27 ZIP codes with lower percentages of Blacks had lower numbers of infections.27

Like others, we also found a higher preponderance of male sex with COVID-19.28 This may be explained, in part, due to hormonal differences. Testosterone has largely suppressive effects on immune function, which may explain the greater susceptibility to infectious diseases observed in men.29 Other postulated mechanisms include male hormone-regulated increased expression of genes encoding for the SARS-CoV-2 entry receptors angiotensin-converting enzyme-2 receptor.30 Furthermore, the behavioral aspects that potentially differ between sexes, such as tobacco use or adherence to hand hygiene, might contribute to differences in risk of COVID-19.9

We found an independent association between the risk of death and HCQ among SOT recipients. This association remained significant even after the IPTW propensity matching of cases with controls. QTc interval was similar in those who received HCQ in the SOT and non-SOT groups. The reason of increased death observed in SOT with use of HCQ likely multifactorial and may be related to drug–drug interactions. We examined the effect of month of admission on death and this was not significant. The preponderance of evidence thus far indicates that HCQ does not have benefit for COVID-19 illness, and has been linked to significant side effects,30,31 with the major HCQ randomized controlled trials (RECOVERY, ORCHID, SOLIDARITY) all terminated due to lack of benefit. Our center stopped using HCQ as a treatment modality for COVID-19 infection by April 4, 2020 because of concern for lack of efficacy for COVID-19 in the literature as mentioned earlier. It is plausible that there might be unmeasured confounding that stayed not captured by inverse probability treatment weighting propensity matching.31,32

The impact of chronic immunosuppression on COVID-19 is not known but is highly relevant, because host inflammatory responses constitute an important cause of associated organ injury. Prior studies have reported elevated biomarkers of inflammation among SOT recipients at presentation.4,21 Despite the chronic immunosuppression, SOT recipients were able to mount a higher inflammatory response than controls and had similar degree of lymphopenia at presentation in our study. This may explain similar incidence of severe disease. The majority of our patients were on calcineurin inhibitors-based regimen, which was continued through their treatment course on the premise that T-cell migration and signaling are needed for cytokine activation33 and, therefore, inhibiting T-cell function would mitigate progression to severe disease. We only had 2 patients in whom calcineurin inhibitor was discontinued because of hyperkalemia and progressive renal failure. We held mycophenolate in almost all of the patients during the course of COVID-19 infection.

The limitation of our is a retrospective study design from a single center which could result in potential bias due to unmeasured patient characteristics and patient selection. Contrarily, our case-control study design provided with matched controls allowed us to compare the COVID-19 outcomes between SOT recipients and non-SOT matched controls with COVID-19. The drug treatment of COVID-19 rapidly evolved during the study period with new clinical trials available to the patients during the latter half of the study period. Although our study did not account for those changes in practices, the management was similar for the cases as well as control given the single center study. Furthermore, we found no significant difference in survival based on admission month.

In conclusion, SOT recipients with COVID-19 are more likely to be males and Blacks. Despite higher baseline and peak inflammatory response and higher need for RRT, the odds of severe COVID-19 and short-term risk of death in SOT recipients with COVID-19 were similar to that of matched nontransplant controls. HCQ use among SOT recipients with COVID-19 was associated with higher risk of death compared to nonuse, calling further into question its role in COVID-19 management.

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