Discussion
Our Study is the first to evaluate the Charlson Comorbidity Index in
adult patients hospitalized with acute respiratory infection secondary
to HMPV and look at its predictive value on mortality in this patient
population. CCI was initially proposed in 1987 and was tested for its
ability to predict risk of death from comorbid disease in a 10-year
follow-up Cohort
(9).
It has been validated in patients with renal cell carcinoma (10) post
radical cystectomy (11) and
internal medicine related complications post hip
arthroplasty (12). It proved to
be good at prediction of long-term functional outcome for the stroke
population
(13). It is also proved to independently predicts short- and long-term
mortality in acutely ill hospitalized elderly adults
(14).
While the CCI was not found to be associated with an increased risk of
mortality in our cohort of HMPV infection, an elevated CCI was shown
recently to predict poor prognosis in hospitalized patient with
coronavirus disease (COVID19) and end stage renal disease on
hemodialysis (15) and in general in patients with COVID 19 in a recent
meta-analysis
(16).
In another study by Setter et al, although the Charlson Comorbidity
Index Score was different between survivors and non survivors in
patients with severe acute respiratory infections, its performance was
not optimal
(17).
In that study most patients studied had influenza pneumonia and few had
HPMV. The low number of patients in our study precludes us to make
strong conclusions regarding the value of CCI, however it was noted that
most patients had a high CCI with a mean of 4.6 which explains the high
mortality rate of 22% which is not unusual and was even reported to be
50% in an outbreak among elderly patients in a long-term care facility
(LTCF) (18).
This mortality rate even exceeds that related to COVID19 in LTCF which
was reported recently to be 14% (153751/1090729) (19). It is worth
noting that unlike COVID19, HMPV causes severe disease in young children
ranging from croup like, asthma exacerbations, bronchiolitis and
pneumonia with a peak age of ranging from 5 to 22 months old which is
older than those with RSV (20). Unlike infections due to
SARS-Cov2, HMPV infections are seasonal with winter epidemics occurring
from December to April in the northern hemisphere at the same time or
just after RSV epidemics. This is likely due to the lower
transmissibility of HMPV which is usually transmitted by contact with
contaminated surfaces as opposed to SARS-Cov2 which is more
transmissible, mainly via respiratory droplets and contact
(21) and possibly airborne (22).
In Our Study we noted that patients requiring ICU care and mechanical
ventilation and those with bacterial or fungal superinfection had worse
outcome and were more likely to die which is not unusual and seen in
patients with influenza and COVID19 as well (23). In addition, having
higher fever and abnormal CXR may indicate a worse outcome. The CXR
findings were similar to what is seen with influenza or RSV lower
respiratory tract infections which is different than radiographic
findings described with COVID19 which are easily recognized due to its
characteristic peripheral distribution
(24). Other features that
distinguish HMPV infection from the COVID19 due to the Omicron variants
specifically is that most patients complained of cough and dyspnea,
85.7% and 71% respectively while rhinorrhea with nasal congestion,
sore throat and myalgia were even less frequently reported in 38%,
14.2% and 23.8% respectively which is usually more prominent with the
Omicron variants of SARS-Cov2 related infections with 70% of patients
presenting with sore throat (25).