Browsing by Author "Chan, Paul K. S."

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Determinants of Antiviral Effectiveness in Influenza Virus a Subtype H5n1
(Oxford Univ Press inc, 2012) Chan, Paul K. S.; Lee, Nelson; Zaman, Mukhtiar; Adisasmito, Wiku; Coker, Richard; Hanshaoworakul, Wanna; Dreyer, Nancy A.
Background. Oseltamivir is widely used as treatment for influenza virus A subtype H5N1 (hereafter, "H5N1") infection but, like any intervention, is not always effective. Methods. We used Avian Influenza Registry data from 10 countries to examine the risk of death in 215 patients with confirmed H5N1 infection who were treated with oseltamivir, according to viral clade, age, respiratory failure, and adjunctive treatment with corticosteroids or antibiotics. Results. The median age of infected individuals was 18 years, and 50% were male. The highest fatality rate occurred in a country with clade 2.1 virus circulation, and the lowest occurred in countries with clade 2.2 virus circulation (P < .001). In univariate analyses, age of <= 5 years and treatment <= 2 days after symptom onset were protective against fatality. When accounting for all risk factors, early initiation of oseltamivir was found to be particularly effective in individuals without respiratory failure (odds ratio, 0.17; P = .04). Patients who had advanced respiratory failure requiring ventilatory support at the time of oseltamivir initiation were more likely to die from the episode of H5N1 infection than patients who did not (P < .001). Adjunctive therapy did not improve the likelihood of surviving the episode. Conclusions. Oseltamivir is especially effective for treating H5N1 infection when given early and before onset of respiratory failure. The effect of viral clade on fatality and treatment response deserves further investigation.
Effectiveness of Antiviral Treatment in Human Influenza A(H5n1) Infections: Analysis of a Global Patient Registry
(Oxford Univ Press inc, 2010) Adisasmito, Wiku; Chan, Paul K. S.; Lee, Nelson; Oner, Ahmet Faik; Gasimov, Viktor; Aghayev, Faik; Toovey, Stephen
Background. Influenza A(H5N1) continues to cause infections and possesses pandemic potential. Methods. Data sources were primarily clinical records, published case series, and governmental agency reports. Cox proportional hazards regression was used to estimate the effect of treatment on survival, with adjustment using propensity scores (a composite measure of baseline variables predicting use of treatment). Results. In total, 308 cases were identified from 12 countries: 41 from Azerbaijan, Hong Kong SAR, Nigeria, Pakistan, and Turkey (from clinical records); 175 from Egypt and Indonesia (from various sources); and 92 from Bangladesh, Cambodia, China, Thailand, and Vietnam (from various publications). Overall crude survival was 43.5%; 60% of patients who received >= 1 dose of oseltamivir alone (OS+) survived versus 24% of patients who had no evidence of anti-influenza antiviral treatment (OS-) (P < .001). Survival rates of OS+ groups were significantly higher than those of OS- groups; benefit persisted with oseltamivir treatment initiation <= 6-8 days after symptom onset. Multivariate modeling showed 49% mortality reduction from oseltamivir treatment. Conclusions. H5N1 causes high mortality, especially when untreated. Oseltamivir significantly reduces mortality when started up to 6-8 days after symptom onset and appears to benefit all age groups. Prompt diagnosis and early therapeutic intervention should be considered for H5N1 disease.
H5n1 Avian Influenza in Children
(Oxford Univ Press inc, 2012) Oner, Ahmet Faik; Dogan, Nazim; Gasimov, Viktor; Adisasmito, Wiku; Coker, Richard; Chan, Paul K. S.; Dreyer, Nancy A.
Background. Avian influenza continues to pose a threat to humans and maintains the potential for greater transmissibility. Understanding the clinical presentation and prognosis in children will help guide effective diagnosis and treatment. Methods. A global patient registry was created to enable systematic collection of clinical, exposure, treatment, and outcomes data on confirmed cases of H5N1. Bivariate and multivariate statistical tools were used to describe clinical presentation and evaluate factors prognostic of survival. Results. Data were available from 13 countries on 193 children <18 years who were confirmed as having been infected with H5N1; 35.2% of cases were from Egypt. The case fatality rate (CFR) for children was 48.7%, with Egypt having a very low pediatric CFR. Overall, children aged <= 5 years had the lowest CFR and were brought to hospitals more quickly and treated sooner than older children. Children who presented for medical care with a complaint of rhinorrhea had a 76% reduction in the likelihood of death compared with those who presented without rhinorrhea, even after statistical adjustment for age, having been infected in Egypt, and oseltamivir treatment (P = .02). Delayed initiation of treatment with oseltamivir increases the likelihood of death, with an overall 75% increase in the adjusted odds ratio for death for each day of delay. Conclusions. The presence of rhinorrhea appears to indicate a better prognosis for children with H5N1, with most patients surviving regardless of age, country, or treatment. For individuals treated with oseltamivir, early initiation of treatment substantially enhances the chance of survival.
Multiple Imputation: Application To a Global Avian Influenza Registry
(Wiley-blackwell, 2011) Swenson, Anna J.; Mack, Christina D.; Dreyer, Nancy A.; Adisasmito, Wiku; Bamgboye, Ebun; Chan, Paul K. S.; Zaman, Mukhtiar
Strengthening Observational Evidence for Antiviral Effectiveness in Influenza a (H5n1)
(Oxford Univ Press inc, 2011) Adisasmito, Wiku; Chan, Paul K. S.; Lee, Nelson; Oner, Ahmet Faik; Gasimov, Viktor; Zaman, Mukhtiar; Toovey, Stephen