Abstract
Human metapneumovirus (HMPV), a common respiratory virus, can cause severe disease in pre- and post-hematopoietic cell transplant (HCT) recipients. We conducted a retrospective cohort analysis in HCT patients with HMPV (N=23) or respiratory syncytial virus (RSV, N=23) detected in bronchoalveolar lavage (BAL) samples by reverse-transcription PCR between 2006 and 2011 to determine disease characteristics and factors associated with outcome. Mortality rates at 100 days were 43% for both HMPV and RSV lower respiratory tract disease (LRTD). Steroid therapy, oxygen requirement > 2L or mechanical ventilation and bone marrow as cell source were significant risk factors for overall and virus-related mortality in multivariable models while the virus type was not. The presence of centrilobular/nodular radiographic infiltrates was a possible protective factor for mechanical ventilation. Thus, HMPV LRTD is associated with high mortality in HCT recipients. Earlier detection in combination with new antiviral therapy is needed to reduce mortality among HCT recipients.
Introduction
Human metapneumovirus (HMPV) is a paramyxovirus closely related to respiratory syncytial virus (RSV). HMPV occurs with a seasonal pattern in the general population every winter and spring. Both HMPV and RSV cause similar symptoms in immunocompetent children and adults and are impossible to distinguish on a clinical basis.(1) HMPV infections can cause severe and even fatal disease in immunocompromised patients(2, 3) with crude reported mortality rates from HMPV pneumonia ranging from 10% to 80% in different small cohort studies of cancer and/or hematopoietic cell transplant (HCT) patients.(3–6) But to date, no study has directly compared LRTD associated with HMPV to that of RSV in immunocompromised patients. Although the treatment and outcome of RSV LRTD in HCT has been relatively well studied and standardized (7, 8), few data are available on the impact of HMPV LRTD during the time surrounding HCT. The purpose of this study was to characterize the clinical and radiographic presentation, viral load and factors associated with outcome of HMPV pneumonia in HCT candidates and recipients and compare results to RSV pneumonia.
Material and Methods
Patients and Samples
We retrospectively reviewed medical charts of all pre- and post- HCT recipients with HMPV or RSV RNA detected in bronchoalveolar lavage (BAL) samples by real-time reverse transcription (RT)-PCR. Molecular analyses on BAL were done clinically in real time starting in January 2006 for HMPV and March 2007 for RSV. This study included patients undergoing BAL with HMPV or RSV detected through February 1st 2011. The RSV cases are a subset of a series reported earlier.(9) Sera and nasal wash specimens that had been collected 11 days before to 11 days after each BAL were retrospectively identified and if not previously tested for these viruses, were evaluated for the presence of HMPV and RSV by RT-PCR. Research was approved by the Institutional Review Board at Fred Hutchinson Cancer Research Center; informed consent was signed by study participants.
Laboratory Method
In addition to RSV and HMPV RT-PCR, respiratory viral diagnosis for multiple respiratory viruses was performed on BAL specimens from pre- and post-HCT recipients according to institutional protocol. Direct fluorescent antibody testing (DFA) for influenza A and B, parainfluenza 1–3, adenovirus and RSV as well as RSV shell vial cultures were performed on BALs between 2006 and 2011 as described in a previously published protocol.(10) HMPV DFA was performed on BALs from February 2008 through 2011. BAL samples were also assessed for broad range of bacterial, fungal and viral pathogens using standard culture and staining methods as well as the aspergillus galactomannan assay.(11, 12)
RT-PCR was performed on BALs, nasal wash and sera specimens according to a previously published protocol.(13) Briefly, total nucleic acids were obtained from 200 μL of each BAL or nasal wash sample by adding 400 μL of lysis buffer. After incubation for 10 min at 60°C, 600μL of isopropanol was added and the samples were centrifuged at 13,000 × g for 15 min. The pellets were washed with 1 mL of 70% ethanol and suspended in 200 μL of RNAse free water. One-step RT-PCR reaction mixtures (TaqMan One-Step RT-PCR Master Mix, Applied Biosystems) were prepared using primers and probes targeting HMPV A/B and an internal control or RSV A/B and an internal control as previously published.(13) The reactions were performed and analyzed in a 7000 Sequence Detection System (Applied Biosystems) under the following conditions: 30 min at 48 °C and 10 mi n at 95 °C, followed by 40 cycles of 15 s at 95 °C and 1 min at 60 °C. Sera extractions were performed using the QIAamp RNA Mini Kit as previously reported and provided a sensitivity of 200 copies/mL for a cutoff of 10 copies/reaction.(14) Cycle threshold (Ct) values were converted into viral loads (copies/mL) of each virus using stored standard curves made of RNA transcripts.
Statistical Methods
Statistical comparisons were performed using Chi-squared test or Fisher’s exact test for categorical variables (as appropriate), and Wilcoxon rank sum test was utilized for continuous variables. The probability of survival was estimated by the Kaplan-Meier method. Univariate and multivariate logistic regression models were used to estimate odds ratio and 95% confidence interval for hypoxemia. Univariate and multivariate Cox regression models were used to evaluate hazard ratio and 95% confidence interval for death by day 100 and virus related death at day 100. Hypoxemia and mechanical ventilation occurring after diagnosis were analyzed as time-dependent variables. All reported p-values were two sided, and considered significant if p<0.05. Analyses were performed using SAS 9.2 (Cary, NC, USA).
Results
Patients
Between January 2006 and February 2011, 23 severely immunocompromised pre- or post-HCT patients had HMPV detected by RT-PCR from BAL. Between March 2007 and February 2011, 23 separate patients were found to have RSV LRTD. Both groups had similar demographic characteristics and levels of immunosuppression (Table 1). All patients infected with RSV (with the exception of one who declined therapy) were treated with aerosolized ribavirin and palivizumab according to our institutional protocol; treatment for HMPV was non-standardized and differed by care provided, as there were no standardized institutional treatment guidelines. Among the 23 patients with HMPV LRTD, 4 received ribavirin alone, 5 received intravenous immunoglobulins (IVIG) alone and 6 received both. Time to treatment after first positive respiratory sample (including nasopharyngeal secretions or BAL) was a median of 5 days (range 1 to 46 days) for HMPV and 1 day (range 0 to 4 days) for RSV (Wilcoxon rank; p=0.0005), and time to treatment after first positive BAL had a median of 2 days (range −13 to 7 days) for HMPV and 0 days (range −15 to 2 days) for RSV (Wilcoxon rank; p=0.009). HMPV and RSV were generally detected between December and June. One RSV cluster occurred during the study period, December 2007, in which BALs from 7 patients tested positive for RSV. A smaller HMPV cluster was identified in May 2007 that included 4 patients with HMPV LRTD. Two additional cases of RSV LRTD occurred during the study period in which BAL samples were not prospectively tested by RT-PCR and no samples were available for retrospective testing. These two patients were not included in this study. All patients with HMPV LRTD were tested by RT-PCR.
Table 1.
Demographic and clinical variables of patients with positive RT-PCR for HMPV or RSV from bronchoalveolar lavages.
| Demographics & Clinical Variables | RSV (n=23) | HMPV (n=23) | p-value |
|---|---|---|---|
| Sex Male (N, %) | 16 (70) | 15 (65) | 0.75 |
| Age (Median years, IQR) | 58 (46–67) | 50 (32–63) | 0.095 |
| HSCT (type) (N, %) | |||
| autologous | 4 (17) | 3 (13) | 0.84 |
| allogeneic | 15 (66) | 14 (61) | |
| pre-HSCT | 4 (17) | 6 (26) | |
| Cell source (N, %) | |||
| bone marrow (BM) | 3 (13) | 6 (26) | 0.43 |
| peripheral blood stem cell (PBSC) | 18 (78) | 13 (57) | |
| cord blood (CB) | 2 (9) | 3 (13) | |
| No transplant | 0 | 1 (4) | |
| TBI1(N, %) | |||
| 12 Gy | 3 (16) | 2 (12) | 0.58 |
| 2 Gy | 9 (47) | 11 (65) | |
| None | 7 (37) | 4 (24) | |
| GVHD2(N, %) | 13 (81) | 11 (79) | 1 |
| Time after HCT1(Median days, IQR) | 106 (17–271) | 80 (20–361) | 0.85 |
| Time after HCT > 100 days1 (N, %) | 10 (53) | 8 (47) | 0.74 |
| Lymphocytes count under 300 cells/μL at time of BAL(N, %) | 9 (39) | 11 (48) | 0.55 |
| CMV reactivation within 1month before BAL1 (N, %) | 7 (37) | 6 (35) | 0.92 |
| Steroids within 2 weeks before BAL (N, %) | 13 (57) | 9 (39) | 0.24 |
| Co-pathogen (N, %) 3 | 8 (35) 4 | 13 (57) 5 | 0.18 |
| Oxygen at diagnosis (>2L+Ventilation) | 11 (48) | 8 (35) | 0.23 |
| Radiologic Variables6 | |||
| centrilobular/nodular (N, %) | 13 (59%) | 8 (36%) | 0.13 |
| ground glass (N, %) | 15 (68%) | 13 (59%) | 0.53 |
| tree in bud (N, %) | 4 (18%) | 4 (18%) | 1 |
| alveolar (N, %) | 14 (64%) | 15 (68%) | 0.75 |
| Treatment variables | |||
| Treatment with ribavirin only (N, %) | 0 (0) | 4 (17) | NA |
| Treatment with ribavirin and IVIG/palivizumab (N, %) | 22 (96) | 6 (26) | NA |
| Treatment with IVIG only (N, %) | 0 (0) | 5 (22) | NA |
| Time to start of treatment from first positive sample (Median days, IQR) | 1 (1–1) | 5 (2–7) | 0.0005 |
| Time to start of treatment from first positive BAL (Median days, IQR) | 0 (−1–1) | 2 (1–5) | 0.009 |
| Outcomes | |||
| Hypoxemia (N, %) | 16 (70%) | 15 (65%) | 0.75 |
| Mechanical ventilation (N, %) | 10 (43%) | 7 (30%) | 0.36 |
| Death at 100 days (N, %) | 10 (43%) | 10 (43%) | 1 |
| Death related to RSV or HMPV infection (N, %) | 8 (35%) | 9 (39%) | 0.76 |
HCT recipients only
allo HCT recipients only
Some patients had more than one pathogen identified in the BAL or in the blood at presentation. When another respiratory virus was identified, RSV or HMPV were always the predominant virus based on viral loads. Fungal infections were determined by blood or BAL galactomanane, microbiology or pathology and most were known and treated at the time of respiratory virus diagnosis.
Fungal (3), S. aureus, enterococcus (3), E. coli, Klebsiella (2), rhinovirus (2), S. viridians sepsis, Klebsiella sepsis.
Pneumocystis jiroveci, Fungal (9), Haemophilus, S. pneumonia, Stenotrophomonas, enterococcus, parainfluenza, influenza A, rhinovirus (3), coronavirus (3), CMV in BAL (2), HSV in BAL, enteroccocus sepsis, staphylococcus sepsis, GNR sepsis, VRE sepsis.
Only 22 of 23 patients with HMPV LRTD and 22 of 23 patients with RSV LRTD had axial tomography performed.
Virologic Results
Because HMPV DFA was not available prior to February 2008, only 14 of the 23 HMPV positive BAL samples were tested by DFA and RT-PCR, whereas 22 of the 23 RSV positive BALs were tested with both methods. Compared to RT-PCR, HMPV DFA had a sensitivity of 71% (10/14) while RSV DFA had a sensitivity of 86% (19/22). The difference between HMPV and RSV mean viral loads in the first BAL sample (6.43 Log10 copies/mL, IQR: 5.79–7.97; and 7.13 Log10 copies/mL IQR: 6.34–8.11, respectively) did not reach statistical significance (Wilcoxon rank; p=0.17).
HMPV was detected by RT-PCR in nasal washes from 10 of 15 patients who had been sampled within 11 days prior to or following the BAL. In comparison, RSV was identified in all 14 patients who had nasal wash samples tested. HMPV LRTD patients who tested negative by nasal wash had lower viral loads in their BAL compared to those who tested positive in the nasal wash (Figure 1a). Sera were obtained from 30 patients (13 infected with HMPV and 17 infected with RSV) within 11 days prior to or following the BAL. In one patient with HMPV LRTD (viral load of 8.19 Log10 copies/mL), HMPV RNA was detected in 2 serum samples taken 4 days apart. We detected RSV RNA in two patients with RSV LRTD (viral load of 8.56 and 7.99 Log10 copies/mL); in one of these two patients, RSV was detected in 4 serum samples over a 10 day period starting the day prior to the BAL until 9 days after. All 3 patients with viral RNA in the sera died of severe respiratory disease (Figure 1b).
Figure 1.
a) RT-PCR results on nasal washes (X) sampled within 11 days before or after the positive bronchoalveolar lavage (BAL). Negative nasal washes were found in 5 patients with HMPV LRTD while all patients with RSV LRTD had at least one positive nasal wash. Negative nasal washes were found in patients with lower BAL viral load. b) RT-PCR results on sera (X) sampled within 11 days before or after the positive BAL. One patient with HMPV LRTD had 2 positive sera (HMPV patient 3) while 2 patients with RSV LRTD had positive sera (RSV patients 2 and 7). All 3 patients with positive sera had a high BAL viral load and died.
Radiologic Results
Radiological features of all 46 patients supported the diagnosis of a viral LRTD. Twenty-two patients with RSV LRTD and 22 with HMPV LRTD underwent high-resolution computed tomography (HRCT) imaging. Centrilobular, ground glass, tree-in-bud and alveolar opacities were found in similar proportions among HMPV- and RSV- infected patients. Centrilobular nodules were associated with less mechanical ventilation in a model that adjusted for virus type (adjusted OR 0.18, 95% CI 0.0–1.8; p=0.027), while ground glass opacities tended to be associated with increased rates of hypoxemia in patients with RSV or HMPV LRTD (adjusted OR 3.00; 95% CI 0.8–11; p=0.1).
Outcome
Patients with HMPV and RSV LRTD had similar rates of hypoxemia and mechanical ventilation at anytime during the episode (Table 1). Two patients with HMPV LRTD refused mechanical ventilation and subsequently died. Mortality rates by day 100 after diagnosis were identical between patients with HMPV and RSV LRTD (43% vs. 43%), and deaths related to the actual viral infection were also similar (39% vs. 35%). The Kaplan-Meier survival estimate is presented in Figure 2a. We detected a higher frequency of co-pathogens in patients with HMPV compared to those with RSV LRTD (57% vs. 35%), however, the difference was not statistically significant (p=0.175).
Figure 2.
Kaplan-Meier Survival Estimates for a) RSV and HMPV LRTD and b) RSV or HMPV LRTD according to steroid dose c) HMPV LRTD treated with ribavirin and untreated.
Risk factors for overall mortality
In univariate Cox regression analyses, there were no statistically significant differences in outcome between HMPV and RSV LRTD. However, stem cell source, steroid treatment, and oxygen use were associated with overall mortality by day 100 in patients with RSV or HMPV LRTD (Table 2). Steroid treatment was also associated with overall mortality in a dose-dependent fashion (Table 2). Similar results were obtained when only HMPV LRTD cases were analyzed (data not shown). Kaplan-Meier survival estimates for patients with HMPV or RSV LRTD according to steroid dose are shown in Figure 2b. In several multivariable models that adjusted for cell source, oxygen requirement, and steroid use, the virus type (RSV vs. HMPV) was not a significant factor for mortality. Steroids at the time of diagnosis of LRTD (adjusted HR 4.1 to 7.9), PBSC or cord blood as cell source (adjusted HR 0.15 to 0.21) and oxygen requirement >2L or mechanical ventilation at diagnosis (adjusted HR 3.6 to 4.6) were significant risk factors in multivariable models. Hypoxemia that occurred after the diagnosis of LRTD (modeled as time-dependent variable) was also associated with death (adjusted HR 5.9, 95% CI 1.3–25.9); p=0.02). Models that included virus type and ribavirin treatment for HMPV (early versus late versus none), type of radiographic presentation, viral load or lymphopenia did not yield statistically significant differences in outcomes between the two viruses nor an association among the HMPV cases alone (data not shown). When ribavirin use was treated as time-dependent variable (to account for possible treatment biases), there was also no detectable beneficial effect (HR 0.99, 95% CI 0.3–2.8). The median time between transplant and diagnosis of HMPV was 18 days in the group treated with ribavirin and 124 days in the untreated group (Table 3). Kaplan-Meier survival estimates for patients with HMPV LRTD who received ribavirin and those who did not are shown in Figure 2c.
Table 2.
Factors associated with overall mortality at day 100 after diagnosis among 46 patients with RSV or HMPV LRTD (univariate analysis).
| Death by Day 100 | ||
|---|---|---|
| Variable | HR (95% C.I.) | p-value |
| Virus (HMPV vs RSV)) | 1.11 (0.5–2.7) | 0.82 |
| HCT (allo vs auto) | 5.16 (0.7–39) | 0.11 |
| GVHD (allo only) | 0.96 (0.3–3.0) | 0.95 |
| Cell source (PBSC vs. BM) | 0.18 (0.07–0.47) | <0.001 |
| Time after HCT (>100 days vs. < day 100) | 2.02 (0.8–5.2) | 0.15 |
| Lymphocyte count at diagnosis (< 300 cell/mm3 vs. < 300 cell/mm3) | 1.95 (0.8–4.7) | 0.14 |
| CMV reactivation at diagnosis (HCT only) | 0.57 (0.2–1.6) | 0.29 |
| Co-pathogens (present vs. absent) | 1.41 (0.6–3.4) | 0.45 |
| Centrilobular/nodular opacities (present vs. absent) | 0.48 (0.2–1.3) | 0.14 |
| Ground glass opacities (present vs. absent) | 1.22 (0.5–3.3) | 0.69 |
| Tree in bud opacities (present vs. absent) | 0.50 (0.1–2.2) | 0.36 |
| Alveolar opacities (present vs. absent) | 1.98 (0.7–6.0) | 0.23 |
| Steroids (any vs none) | 4.99 (1.8–14) | 0.002 |
| Steroids (< 1 mg/kg vs none) | 3.80 (1.2–12) | 0.02 |
| Steroids (≥ 1mg/kg vs none) | 7.12 (2.3–22) | <0.001 |
| Viral load in BAL (above vs below 3rd quartile) | 0.79 (0.3–2.4) | 0.68 |
| Oxygen requirement at diagnosis (> 2L/mechanical ventilation vs. no/≤ 2L) | 3.56 (1.41–8.99) | 0.007 |
| Hypoxemia after diagnosis (time-dependent) | 6.31 (1.46–27.2) | 0.0014 |
| Mechanical ventilation after diagnosis (time-dependent) | 10.7 (4.04–28.2) | <0.001 |
Table 3.
Characteristics of 23 patients with HMPV lower respiratory tract disease, according to ribavirin therapy.
| Characteristic | Treated with ribavirin (n=10) | No ribavirin (n=13) |
|---|---|---|
| Underlying disease | ||
| Acute leukemia | 4 (40%) | 4 (31%) |
| HD/MM/NHL | 3 (30%) | 6 (46%) |
| CML | 1 (10%) | 0 (0%) |
| CLL | 0 (0%) | 3 (23%) |
| Other | 2 (20%) | 0 (0%) |
| Donor type | ||
| Matched related | 1 (10%) | 1 (8%) |
| Mismatched/unrelated | 5 (50%) | 7 (55%) |
| Autologous | 1 (10%) | 2 (15%) |
| Pre-transplant | 3 (30%) | 3 (22%) |
| Acute GVHD * | 3 (50%) | 7 (88%) |
| Median days post HCT * | 18 | 124 |
| Ventilated at diagnosis | 3 (30%) | 2 (15%) |
HD, Hodgkin disease; MM, multiple myeloma; NHL, non-hodgkin lymphoma; CML, chronic myelogenous leukemia, CLL, chronic lymphocytic leukemia; GVHD, graft-versus-host disease; HCT, hematopoietic cell transplantation
Allogeneic recipients only
Risk factors for virus-related death
Variables from Table 2 were also assessed as possible risk factors for virus-related mortality. There was no difference between the two viruses while steroid use, oxygen use >2L or mechanical ventilation, hypoxemia after diagnosis (time-dependent variable), and cell source remained significant predictors of poor outcome (data not shown). Centrilobular/nodular infiltrates also tended to be protective (adjusted OR 0.35, 95% CI 01–1.2, p=0.08). Ribavirin treatment was not protective. Late use of ribavirin tended to be associated with poorer outcome (adjusted OR 4.0, 95% CI 0.9–17; p=0.06).
Risk factors for hypoxemia and mechanical ventilation
An analysis of candidate variables (Table 2) for an association with hypoxemia or mechanical ventilation showed a trend towards more hypoxemia with ground glass infiltrates (adjusted OR 2.97, 95% CI 0.8–11, p=0.1). Centrilobular/nodular infiltrates were protective in a model that adjusted for virus type (adjusted OR 0.18, 95% CI 0.0–0.8, p=0.027). Ribavirin use was associated with hypoxemia (data not shown).
Discussion
HMPV may cause upper or lower respiratory tract infections in severely immunocompromised HCT recipients both prior to and following transplantation. Asymptomatic shedding of HMPV from the upper respiratory tract has been reported previously, indicating that not all infections with HMPV necessarily result in severe lower tract disease.(15–17) Studies have shown that 27–41% of HMPV upper respiratory tract infection (URTI) will progress to LRTD but the outcome of lower respiratory tract disease is poorly described.(18) We compared recent cases of RSV and HMPV LRTD based on RT-PCR results of BAL samples with evaluation of diagnostic test performance, clinical and radiographic presentation and factors associated with poor outcome. Our study found an overall similarly poor outcome of HMPV and RSV pneumonia and identified use of steroids as an important factor associated with outcome.
Given the virologic similarities of RSV and HMPV, it is not surprising that clinical outcomes are similar between these viruses. However, in this study nearly all cases of RSV pneumonia were treated with ribavirin while only half of patients with HMPV pneumonia received treatment. Comparison of outcomes between treated and untreated patients with HMPV LRTD in this non-randomized, retrospective review did not show any benefit of the drug. This is possibly related to the increased time to treatment observed in patients with HMPV LRTD compared to RSV LRTD, the potential for more aggressive therapy in sicker patients, and the shorter time between transplantation and HMPV diagnosis in the treated group of patients with HMPV LRTD compared to the untreated group. We adjusted for possible confounders such as the degree of acute lung injury (measured by the degree of oxygen requirement) and analyzed ribavirin use as a time-dependent variable to account for difference of the start time of the drug between patients. Nevertheless, the non-randomized nature of the treatment remains a key limitation.
In vitro studies and animal models have shown the efficacy of ribavirin against HMPV.(19, 20) However, no clinical studies have been conducted to evaluate treatment of HMPV LRTD in HCT. Initiation of treatment at the earlier stage of URTI for RSV infection has been shown to improve the outcome and reduces the progression to LRTD.(7) The only prospective randomized study in immunocompromised patients showed a decline of RSV viral load and progression to LRTD but the study was ended prematurely and statistical significance was not reached.(21) HMPV infection has similar rates of progression to LRTD and similar mortality compared to RSV, suggesting preemptive treatment at earlier stages might potentially be useful. New antiviral drugs are needed for both RSV and HMPV and prospective studies are needed to examine whether preemptive therapy at the URTI stage is effective in preventing progression to lower tract disease.
Although lymphopenia is a well-known risk factor for progression to LRTD in viral infections, we were not able to show an impact of lymphocyte counts on mortality.(22, 23) However, we identified steroid treatment, stem cell source and need for oxygen or mechanical ventilation as significant predictors for death. Steroids were primarily administered for non-pulmonary GVHD treatment. Identifying steroid treatment and particularly high dose steroid treatment as a major risk factor for death might help target patients for interventions, including rapid steroid taper or antiviral treatments in the future.
Viral pneumonia in HCT recipients typically presents with small poorly defined centrilobular nodules, tree-in-bud opacities, ground glass opacities and consolidation.(24, 25) These patterns can be present in various amounts in viral pneumonia, including HMPV and RSV.(26, 27) Our study, which represents the first comparison of RSV and HMPV viral pneumonia in HCT, documented similar radiologic features for both infections. As previously reported, ground glass opacity and centrilobular nodules were very common in RSV (68% and 59%, respectively) and HMPV LRTD (59% and 36%, respectively). Tree-in-bud infiltrates were less common (18% for both viruses). A significant proportion of patients also demonstrated alveolar consolidation (64% for RSV and 68% for HMPV), corresponding to more extensive damage on histological examination.(28) Our study correlated radiographic appearance with outcome demonstrating trends for better survival in patients with centrilobular nodules and worse prognosis in patients with ground glass infiltrates which represent a more diffused disease. In addition to detection of viral RNA in serum, this information could be useful in managing patients and identifying those who could benefit from therapy. Viral RNA was detected in the sera of one patient with HMPV LRTD and 2 patients with RSV LRTD; all three died of severe disease, a correlation previously suggested in an earlier study.(14) We speculate that detection of viral RNA in serum samples could become a useful tool to predict or stratify the likelihood of short term survival in patients with HMPV or RSV LRTD. Larger studies are needed to address this question.
We conclude that HMPV LRTD is associated with high mortality rates after HCT. Use of corticosteroids, stem cell source as well as oxygen requirement at baseline and thereafter were associated with poor outcome. The association of poor outcome with high steroid doses suggests a possible intervention, i.e. tapering steroid dose if clinically possible. This should be studied prospectively. Although this is the largest series of HMPV LRTD in HCT recipients, the effect of ribavirin could not be conclusively determined due to small sample size and confounding effects that led to the use of the drug. However, initial results did not suggest a major effect. Larger studies are needed to examine effects of current and future treatment options, optimally in a randomized fashion.
Acknowledgments
We thank the UW molecular virology laboratory technologists and Terry Stevens-Ayers for their help doing the laboratory analysis.
Grant support; National Institutes of Health (CA18029, HL093294, HL081595, CA15704)
Footnotes
Conflict of Interest Disclosures
J.A.E. received research funding from Novartis, MedImmune Inc, and ADMA. M.B. received research funding from ADMA and served as a consultant to Gilead and Microbiotix. The remaining authors declare no competing financial interests.
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