Diphtheria
Thanks to vaccination, respiratory diphtheria has almost disappeared from many European countries. In total, 85% of patients suffer from subclinical disease or turn into asymptomatic carriers (Vitek, 1998) and only an estimated 15% of infections lead to a symptomatic case. The duration of acute illness was based on the Ontario Burden of Infectious Disease Study [AC1] (‘the Ontario Study’) [SW2] and set at 12 days (Kwong, 2012).
Risk of complications
Systemic toxicity (a toxic form of the disease with swelling of the neck) occurs in 8.1% of all diphtheria patients and may lead to complications such as myocarditis, neuropathies and renal failure (Rakhmanova, 1996). The more frequent complications of acute illness are myocarditis and polyneuropathies/nerve palsies. Other complications, such as sepsis, septic arthritis, pneumonia, otitis media, splenic and hepatic abscesses and rhinitis, were not included in the outcome tree because they are either extremely rare or mild.
Our model is based on the assumption that 8.1% of symptomatic patients would have a complicated form of the disease (Rakhmanova, 1996).
Permanent disability following myocarditis (arrhythmias)
Assuming that myocarditis represents 66.6% of the complicated diphtheria cases (Jayashree, 2006) and that 0.25% (Mandell, 1999) of these will develop permanent conduction defects (arrhythmias), the transition probability of patients with complications developing permanent cardiac disability is 0.17%.
Case fatality ratio
The US Centers for Disease Control and Prevention (US CDC) have reported a case-fatality proportion (CFP) of 5–10% for diphtheria, with higher death rates (up to 20%) among persons under five and over 40 years. The case fatality proportion has changed very little over the last 50 years (CDC, 2009).
In the model, the CFP associated with uncomplicated disease is 1% and with complicated disease 25.7% (Rakhmanova, 1996).
Model input summary
Table 1. Transition probabilities used in the outcome tree
Health
outcome |
Distribution of health states in health outcome |
Transition probability |
Source/assumption |
Symptomatic infection (Uncomplicated) (Complicated) |
91.9% 8.1% |
|
Rakhmanova, 1996 |
Permanent disability (arrhythmias) following complicated symptomatic infection |
|
0.17% |
Jayashree, 2006; Mandell, 1999 |
Fatal cases following uncomplicated symptomatic infection |
|
1% |
Rakhmanova, 1996 |
Fatal cases following complicated symptomatic infection |
|
25.7% |
Rakhmanova, 1996 |
Table 2. Disability weights and duration
Health outcome |
Disability Weight (DW) (Haagsma, 2015) |
Duration |
||
DW |
Label |
In years |
Source |
|
Symptomatic infection (Uncomplicated)
(Complicated) |
0.051 (0.039-0.06)
0.125 (0.104-0.152) |
Infectious disease, acute episode, moderate Infectious disease, acute episode, severe |
0.003 |
Kwong 2012 |
Permanent disability (arrhythmias) following complicated symptomatic infection |
0.295 (0.258-0.343) |
Cardiac conduction disorders and cardiac dysrhythmias |
Remaining life expectancy |
|
References
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