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Likely health outcomes for untreated acute febrile illness in the tropics in decision and economic models; a Delphi survey.

Lubell Y, Staedke SG, Greenwood BM, Kamya MR, Molyneux M, Newton PN, Reyburn H, Snow RW, D'Alessandro U, English M, Day N, Kremsner P, Dondorp A, Mbacham W, Dorsey G, Owusu-Agyei S, Maitland K, Krishna S, Newton C, Pasvol G, Taylor T, von Seidlein L, White NJ, Binka F, Mills A, Whitty CJ - PLoS ONE (2011)

Bottom Line: Widely diverse opinions can lead to conflicting outcomes in models they inform.However, opinions varied widely for most parameters, and did not converge on resurveying.The diversity of expert opinion should be recognised when policy options are debated.

View Article: PubMed Central - PubMed

Affiliation: London School of Hygiene & Tropical Medicine, London, United Kingdom. yoel@tropmedres.ac

ABSTRACT

Background: Modelling is widely used to inform decisions about management of malaria and acute febrile illnesses. Most models depend on estimates of the probability that untreated patients with malaria or bacterial illnesses will progress to severe disease or death. However, data on these key parameters are lacking and assumptions are frequently made based on expert opinion. Widely diverse opinions can lead to conflicting outcomes in models they inform.

Methods and findings: A Delphi survey was conducted with malaria experts aiming to reach consensus on key parameters for public health and economic models, relating to the outcome of untreated febrile illnesses. Survey questions were stratified by malaria transmission intensity, patient age, and HIV prevalence. The impact of the variability in opinion on decision models is illustrated with a model previously used to assess the cost-effectiveness of malaria rapid diagnostic tests. Some consensus was reached around the probability that patients from higher transmission settings with untreated malaria would progress to severe disease (median 3%, inter-quartile range (IQR) 1-5%), and the probability that a non-malaria illness required antibiotics in areas of low HIV prevalence (median 20%). Children living in low transmission areas were considered to be at higher risk of progressing to severe malaria (median 30%, IQR 10-58%) than those from higher transmission areas (median 13%, IQR 7-30%). Estimates of the probability of dying from severe malaria were high in all settings (medians 60-73%). However, opinions varied widely for most parameters, and did not converge on resurveying.

Conclusions: This study highlights the uncertainty around potential consequences of untreated malaria and bacterial illnesses. The lack of consensus on most parameters, the wide range of estimates, and the impact of variability in estimates on model outputs, demonstrate the importance of sensitivity analysis for decision models employing expert opinion. Results of such models should be interpreted cautiously. The diversity of expert opinion should be recognised when policy options are debated.

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Related in: MedlinePlus

Probability of developing severe illness for untreated malaria cases.The top panel shows results for low transmission or epidemic prone areas; the bottom panel are the results for medium/high transmission areas. The median in both settings decreases with age and the estimates also become less dispersed.
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pone-0017439-g001: Probability of developing severe illness for untreated malaria cases.The top panel shows results for low transmission or epidemic prone areas; the bottom panel are the results for medium/high transmission areas. The median in both settings decreases with age and the estimates also become less dispersed.

Mentions: The Delphi survey results for children under five years of age are summarized in Tables 1a and 1b and for adults in Tables 2a and 2b. Children in low transmission areas were considered to be at higher risk of progressing to severe malaria (median 30% IQR 10–58%) than those living in areas of higher transmission (median 13% IQR 7–30%), but there was wide variability in the actual prediction. The probability that severe malaria would progress to death was judged similar in both settings (medians 73% and 60% respectively). The likelihood that non-malarial illnesses would require antibiotic treatment, and the outcome of untreated bacterial illnesses, were believed to vary with HIV prevalence. Children living in areas of high HIV prevalence were considered by most participants to be at higher risk of bacterial illness that would benefit from antibiotic treatment, and at greater risk of progressing to severe illness and death if such illnesses went untreated, than children from areas with lower HIV prevalence. The survey results indicated a wide dispersion of expert opinion on almost all parameters best seen in Figures 1–5, with little convergence between rounds of questioning.


Likely health outcomes for untreated acute febrile illness in the tropics in decision and economic models; a Delphi survey.

Lubell Y, Staedke SG, Greenwood BM, Kamya MR, Molyneux M, Newton PN, Reyburn H, Snow RW, D'Alessandro U, English M, Day N, Kremsner P, Dondorp A, Mbacham W, Dorsey G, Owusu-Agyei S, Maitland K, Krishna S, Newton C, Pasvol G, Taylor T, von Seidlein L, White NJ, Binka F, Mills A, Whitty CJ - PLoS ONE (2011)

Probability of developing severe illness for untreated malaria cases.The top panel shows results for low transmission or epidemic prone areas; the bottom panel are the results for medium/high transmission areas. The median in both settings decreases with age and the estimates also become less dispersed.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3044764&req=5

pone-0017439-g001: Probability of developing severe illness for untreated malaria cases.The top panel shows results for low transmission or epidemic prone areas; the bottom panel are the results for medium/high transmission areas. The median in both settings decreases with age and the estimates also become less dispersed.
Mentions: The Delphi survey results for children under five years of age are summarized in Tables 1a and 1b and for adults in Tables 2a and 2b. Children in low transmission areas were considered to be at higher risk of progressing to severe malaria (median 30% IQR 10–58%) than those living in areas of higher transmission (median 13% IQR 7–30%), but there was wide variability in the actual prediction. The probability that severe malaria would progress to death was judged similar in both settings (medians 73% and 60% respectively). The likelihood that non-malarial illnesses would require antibiotic treatment, and the outcome of untreated bacterial illnesses, were believed to vary with HIV prevalence. Children living in areas of high HIV prevalence were considered by most participants to be at higher risk of bacterial illness that would benefit from antibiotic treatment, and at greater risk of progressing to severe illness and death if such illnesses went untreated, than children from areas with lower HIV prevalence. The survey results indicated a wide dispersion of expert opinion on almost all parameters best seen in Figures 1–5, with little convergence between rounds of questioning.

Bottom Line: Widely diverse opinions can lead to conflicting outcomes in models they inform.However, opinions varied widely for most parameters, and did not converge on resurveying.The diversity of expert opinion should be recognised when policy options are debated.

View Article: PubMed Central - PubMed

Affiliation: London School of Hygiene & Tropical Medicine, London, United Kingdom. yoel@tropmedres.ac

ABSTRACT

Background: Modelling is widely used to inform decisions about management of malaria and acute febrile illnesses. Most models depend on estimates of the probability that untreated patients with malaria or bacterial illnesses will progress to severe disease or death. However, data on these key parameters are lacking and assumptions are frequently made based on expert opinion. Widely diverse opinions can lead to conflicting outcomes in models they inform.

Methods and findings: A Delphi survey was conducted with malaria experts aiming to reach consensus on key parameters for public health and economic models, relating to the outcome of untreated febrile illnesses. Survey questions were stratified by malaria transmission intensity, patient age, and HIV prevalence. The impact of the variability in opinion on decision models is illustrated with a model previously used to assess the cost-effectiveness of malaria rapid diagnostic tests. Some consensus was reached around the probability that patients from higher transmission settings with untreated malaria would progress to severe disease (median 3%, inter-quartile range (IQR) 1-5%), and the probability that a non-malaria illness required antibiotics in areas of low HIV prevalence (median 20%). Children living in low transmission areas were considered to be at higher risk of progressing to severe malaria (median 30%, IQR 10-58%) than those from higher transmission areas (median 13%, IQR 7-30%). Estimates of the probability of dying from severe malaria were high in all settings (medians 60-73%). However, opinions varied widely for most parameters, and did not converge on resurveying.

Conclusions: This study highlights the uncertainty around potential consequences of untreated malaria and bacterial illnesses. The lack of consensus on most parameters, the wide range of estimates, and the impact of variability in estimates on model outputs, demonstrate the importance of sensitivity analysis for decision models employing expert opinion. Results of such models should be interpreted cautiously. The diversity of expert opinion should be recognised when policy options are debated.

Show MeSH
Related in: MedlinePlus