Invited contribution: An objective approach to the development of short-term tests predictive of carcinogenicity

The Carcinogenicity Prediction and Battery Selection procedure was developed to address two problems: (1) the identification of highly predictive, yet cost-effective, batteries of short-term tests and (2) the objective prediction of the potential carcinogenicity of chemicals based upon the results of short-term tests even when a mixture of positive and negative results is obtained. In the present report the usefulness of the Carcinogenicity Prediction and Battery Selection procedure is demonstrated using benzo[a]pyrene, benzoin and diethylstilbestrol as examples. In addition, its applicability in the analysis of all the possible outcomes of a battery is illustrated together with an analysis of the worth of additional testing.Abbreviations B[a]P benzo[a]pyrene - CASE Computer-Automated Structure Evaluation - CPBS Carcinogenicity Prediction and Battery Selection - DEHP diethylhexylphthalate - DES diethylstilbestrol - NTA nitrilotriacetate - TCDD 2,3,7,8-tetrachlorodibenzo-p-dioxin     

Genetic activity profiles and pattern recognition in test battery selection

Computer-generated genetic activity profiles and pairwise matching procedures may aid in the selection of the most appropriate short-term bioassays to be used in test batteries for the evaluation of the genotoxicity of a given chemical or group of chemicals. Selection of test batteries would be based on a quantitative comparative assessment of the past performance of similar tests applied to other chemicals of the same structural group. The information potentially available for test-battery selection through the use of this pattern-recognition technique is considerably greater than the qualitative results obtained from individual short-term tests. Application of the method should further our understanding of the relationships between chemical properties and genotoxic responses obtained in short-term bioassays and also may contribute to our knowledge of the mechanisms of complex processes such as carcinogenesis. This approach to battery selection should be augmented by careful consideration of established principles of genetic toxicity testing; that is, a chemical should be evaluated in a battery of tests representing the full range of relevant genetic endpoints.     

The carcinogenicity prediction and battery selection (CPBS) method: a Bayesian approach

Recently, a large number of relatively inexpensive in vitro short-term tests have been developed to help predict the carcinogenicity of chemicals. The carcinogenicity prediction and battery selection (CPBS) method utilizes the results of such short-term tests to screen for chemicals that are most likely to cause cancer. The method is an integrated approach for analyzing large, often sparsely filled, data bases containing short-term test results, which often have only marginal representation of known non-carcinogens. The CPBS method is developed for the purpose of (i) determining the reliability and predictive capability of individual and batteries of short-term tests, and (ii) developing a strategy for formulating and selecting optimally preferred batteries of short-term tests for screening chemicals for further testing. The term 'optimally preferred' connotes the best acceptable combination of tests in terms of trade-offs among the multiple attributes of each test and resulting battery (e.g., cost, sensitivity, specificity, etc). The CPBS method consists of 5 major tasks: (1) data consolidation, (2) parameter estimation, (3) predictivity calculation, (4) battery selection and (5) risk assessment. Although there is a great need for more research and improvement, the CPBS method at its present stage should add an important method to the maze of the thousands of new chemicals that are introduced into drugs, foods, consumer goods and to the environment every year. This method should also provide an enhanced identification procedure for classifying chemicals more accurately as suspected carcinogens or non-carcinogens.     

Artificial intelligence and Bayesian decision theory in the prediction of chemical carcinogens

Two procedures for predicting the carcinogenicity of chemicals are described. One of these (CASE) is a self-learning artificial intelligence system that automatically recognizes activating and/or deactivating structural subunits of candidate chemicals and uses this to determine the probability that the test chemical is or is not a carcinogen. If the chemical is predicted to be carcinogen, CASE also projects its probable potency.

The second procedure (CPBS) uses Bayesian decision theory to predict the potential carcinogenicity of chemicals based upon the results of batteries of short-term assays. CPBS is useful even if the test results are mixed (i.e. both positive and negative responses are obtained in different genotoxic assays). CPBS can also be used to identify highly predictive as well as cost-effective batteries of assays.

For illustrative purposes the ability of CASE and CPBS to predict the carcinogenicity of a carcinogenic and a non-carcinogenic polycyclic aromatic hydrocarbon is shown. The potential for using the two methods in tandem to increase reliability and decrease cost is presented.     

Short-term testing--are we looking at wrong endpoints?

Short-term testing has been performed and interpreted on the basis of correlation between these tests and animal carcinogenicity. This empirical approach has been the only feasible one, due to a lack of knowledge of the actual genetic endpoints of relevance in carcinogenicity. However, the rapidly growing information on genetic alterations actually involved in carcinogenicity and in particular activation of oncogenes, provides facts of basic importance for the strategy of short-term testing. The presently used sets of short-term tests focus on standard genetic endpoints, mainly point mutations and chromosomal aberrations. Little attention has been paid in that connection to other endpoints, which have been shown or suspected to play an important role in carcinogenicity. These endpoints include gene amplification, transpositions, hypomethylation, polygene mutations and recombinogenic effects. Furthermore, indirect effects, for instance via radical generation and an imbalance of the nucleotide pool, may be of great significance for the carcinogenic and cocarcinogenic effects of many chemicals. Modern genetic and molecular technology has opened entirely new prospects for identifying genetic alterations in tumours and in its turn these prospects should be taken advantage of in order to build up more sophisticated batteries of assays, adapted to the genetic endpoints actually demonstrated to be involved in cancer induction. Development of new assay systems in accordance with the elucidation of genetic alterations in carcinogenicity will probably constitute one of the most important areas in genetic toxicology in the future. From a regulatory point of view the prerequisite for a development in this direction will be a flexibility of the handling of questions concerning short-term testing also at a bureaucratic level.     

The influence of the proportion of carcinogens on the cost-effectiveness of short-term tests

The cost-effectiveness of using short-term genotoxicity tests to screen unknown chemicals for carcinogenicity depends upon the inherent reliability of the tests (sensitivity, or fraction of carcinogens giving positive results, and specificity, or fraction of non-carcinogens giving negative results) and also upon the proportion of carcinogens in the population of chemicals to be screened. Individual tests may be combined into batteries to improve reliability; however, this requires decision rules to declare the overall result positive or negative. A framework for developing such rules based upon minimizing costs of false-positives and false-negatives was presented in a seminal paper by Lave and Omenn (1986, Nature (London), 324, 29-34). We have extended their work, which is based on logit analysis, to consider, using Bayes' theorem, the influence of the proportion of carcinogens upon the decision rules for declaring a battery result positive or negative. If the proportion of carcinogens is high (20% or greater), then the most effective tests are those with high sensitivity, and if the proportion of carcinogens is low, then the most effective tests are those with high specificity.     

Strategy for genotoxicity testing: hazard identification and risk assessment in relation to in vitro testing

This report summarizes the proceedings of the September 9-10, 2005 meeting of the Expert Working Group on Hazard Identification and Risk Assessment in Relation to In Vitro Testing, part of an initiative on genetic toxicology. The objective of the Working Group was to develop recommendations for interpretation of results from tests commonly included in regulatory genetic toxicology test batteries, and to propose an appropriate strategy for follow-up testing when positive in vitro results were obtained in these assays. The Group noted the high frequency of positive in vitro findings in the genotoxicity test batteries with agents found not to be carcinogenic and thought not to pose a carcinogenic health hazard to humans. The Group agreed that a set of consensus principles for appropriate interpretation and follow-up testing when initial in vitro tests are positive was needed. Current differences in emphasis and policy among different regulatory agencies were recognized as a basis of this need. Using a consensus process among a balanced group of recognized international authorities from industry, government, and academia, it was agreed that a strategy based on these principles should include guidance on: (1) interpretation of initial results in the "core" test battery; (2) criteria for determining when follow-up testing is needed; (3) criteria for selecting appropriate follow-up tests; (4) definition of when the evidence is sufficient to define the mode of action and the relevance to human exposure; and (5) definition of approaches to evaluate the degree of health risk under conditions of exposure of the species of concern (generally the human). A framework for addressing these issues was discussed, and a general "decision tree" was developed that included criteria for assessing the need for further testing, selecting appropriate follow-up tests, and determining a sufficient weight of evidence to attribute a level of risk and stop testing. The discussion included case studies based on actual test results that illustrated common situations encountered, and consensus opinions were developed based on group analysis of these cases. The Working Group defined circumstances in which the pattern and magnitude of positive results was such that there was very low or no concern (e.g., non-reproducible or marginal responses), and no further testing would be needed. This included a discussion of the importance of the use of historical control data. The criteria for determining when follow-up testing is needed included factors, such as evidence of reproducibility, level of cytotoxicity at which an increased DNA damage or mutation frequency is observed, relationship of results to the historical control range of values, and total weight of evidence across assays. When the initial battery is negative, further testing might be required based on information from the published literature, structure activity considerations, or the potential for significant human metabolites not generated in the test systems. Additional testing might also be needed retrospectively when increase in tumors or evidence of pre-neoplastic change is seen. When follow-up testing is needed, it should be based on knowledge about the mode of action, based on reports in the literature or learned from the nature of the responses observed in the initial tests. The initial findings, and available information about the biochemical and pharmacological nature of the agent, are generally sufficient to conclude that the responses observed are consistent with certain molecular mechanisms and inconsistent with others. Follow-up tests should be sensitive to the types of genetic damage known to be capable of inducing the response observed initially. It was recognized that genotoxic events might arise from processes other than direct reactivity with DNA, that these mechanisms may have a non-linear, or threshold, dose-response relationship, and that in such cases it may be possible to determine an exposure level below which there is negligible concern about an effect due to human exposures. When a test result is clearly positive, consideration of relevance to human health includes whether other assays for the same endpoint support the results observed, whether the mode or mechanism of action is relevant to the human, and - most importantly - whether the effect observed is likely to occur in vivo at concentrations expected as a result of human exposure. Although general principles were agreed upon, time did not permit the development of recommendations for the selection of specific tests beyond those commonly employed in initial test batteries.     

Deployment of short-term assays for the detection of carcinogens; genetic and molecular considerations

The deployment of short-term assays for the detection of carcinogens inevitably has to be based on the genetic alterations actually involved in carcinogenesis. This paper gives an overview of oncogene activation and other mutagenic events connected with cancer induction. It is emphasized that there are indications of DNA alterations in carcinogenicity, which are not in accordance with "conventional" mutations and mutation frequencies, as measured by short-term assays of point mutations, chromosome aberrations and numerical chromosome changes. This discrepancy between DNA alterations in carcinogenicity and the endpoints of short-term assays in current use include transpositions, insertion mutations, polygene mutations, gene amplifications and DNA methylations. Furthermore, tumourigenicity may imply an induction of a genetic instability, followed by a cascade of genetic alterations. The evaluation of short-term assays for carcinogenesis mostly involves two correlations that is, between mutation and animal cancer data on the one hand and between animal cancer data and human carcinogenicity on the other. It should be stressed that animal bioassays for cancer in general imply tests specifically for the property of chemicals to function as complete carcinogens, which may be a rather poor reflection of the actual situation in human populations. The primary aim of short-term mutagenicity assays is to provide evidence as to whether a compound can be expected to cause mutations in humans, and such evidence has to be considered seriously even against a background of negative cancer data. For the evaluation of data from short-term assays the massive amount of empirical data from different assays should be used and new computer systems in that direction can be expected to provide improved predictions of carcinogenicity.     

Clean Recycling of Lead-Acid Batteries for Electric Vehicles: A Reply to Socolow and Thomas

This article is stimulated by the analysis of Socolow and Thomas in the first issue of this journal. Our work showed that a lead-acid battery-powered electric vehicle (Ev) would result in more lead being discharged into the environment than a comparable car burning leaded gasoline. Five hundred thousand EVs would lead to a 20% increase in lead use in the United States, and presumably a comparable 20% increase in lead discharges.
The Socolow-Thomas analysis asserts: (I) choosing not to pursue technology that uses toxic materials will unduly constrain the research and development (R&D) in advanced vehicles and limit the options likely to emerge from that research; (2) we do not do a full risk assessment of the lead discharges from lead smelting, battery making and recycling; and (3) in response to regulation the industry might devise a "clean recycling" system.
We doubt the wisdom of increasing R&D on lead batteries because introducing large quantities of lead into cars will pose health risks. The possibility of clean recycling in the future is not an adequate basis for mandating EVs. Proponents of EVs should prove there is no harm to the environment Regulators should not require EVs until there is a reasonable showing of environmental benefit and that the requirement is cost-effective in reducing ozone.     

The diffusion of new genetic tests for predicting disease.

This paper examines the pathways by which new genetic tests will become available to the public. In view of the scarcity of genetic specialists, the pathway is likely to involve primary care physicians. Other pathways entail state-mandated testing, community-based programs, or testing by laboratories without much involvement of primary care physicians. When testing does become available the "destination" will be either family-centered testing or population-oriented screening. The deterrent to screening will not be the inability to detect disease-causing mutations but the costs and attitudes of providers and the public. When tests are provided primarily to provide information about risks to future children, some people will oppose screening on religious or moral grounds. When there are no inexpensive treatments, some will fear that insurance companies and employers will use tests to deny them health care coverage. Some may not want to know their risks for disorders about which little can be done. For common, multifactorial disorders, genetic tests will have low predictive value. Because of these problems, the decision to be tested, regardless of the destination, requires that "testees" be fully informed and consent to testing. When acceptance rates are low, screening is less likely to be cost-effective; family-centered testing becomes the default destination.     

Cost-effective designs for linkage disequilibrium mapping of complex traits

The current development of densely spaced collections of single nucleotide polymorphisms (SNPs) will lead to genomewide association studies for a wide range of diseases in many different populations. Determinations of the appropriate number of SNPs to genotype involve a balancing of power and cost. Several variables are important in these determinations. We show that there are different combinations of sample size and marker density that can be expected to achieve the same power. Within certain bounds, investigators can choose between designs with more subjects and fewer markers or those with more markers and fewer subjects. Which designs are more cost-effective depends on the cost of phenotyping versus the cost of genotyping. We show that, under the assumption of a set cost for genotyping, one can calculate a "threshold cost" for phenotyping; when phenotyping costs per subject are less than this threshold, designs with more subjects will be more cost-effective than designs with more markers. This framework for determining a cost-effective study will aid in the planning of studies, especially if there are choices to be made with respect to phenotyping methods or study populations.     

Blood volume-monitored regulation of ultrafiltration in fluid-overloaded hemodialysis patients: study protocol for a randomized controlled trial

Background

Governments and donors all over Africa are searching for sustainable, affordable and cost-effective ways to improve the quality of malaria case management. Widespread deficiencies have been reported in the prescribing and counselling practices of health care providers treating febrile patients in both public and private health facilities. Cameroon is no exception with low levels of adherence to national guidelines, the frequent selection of non-recommended antimalarials and the use of incorrect dosages. This study evaluates the effectiveness and cost-effectiveness of introducing two different provider training packages, alongside rapid diagnostic tests (RDTs), designed to equip providers with the knowledge and practical skills needed to effectively diagnose and treat febrile patients. The overall aim is to target antimalarial treatment better and to facilitate optimal use of malaria treatment guidelines.

Methods/Design

A 3-arm stratified, cluster randomized trial will be conducted to assess whether introducing RDTs with provider training (basic or enhanced) is more cost-effective than current practice without RDTs, and whether there is a difference in the cost effectiveness of the provider training interventions. The primary outcome is the proportion of patients attending facilities that report a fever or suspected malaria and receive treatment according to malaria guidelines. This will be measured by surveying patients (or caregivers) as they exit public and mission health facilities. Cost-effectiveness will be presented in terms of the primary outcome and a range of secondary outcomes, including changes in provider knowledge. Costs will be estimated from a societal and provider perspective using standard economic evaluation methodologies.

Trial Registration

ClinicalTrials.gov: NCT00981877     

Assembly and preliminary analysis of a genotoxicity data base for predicting carcinogens

With a view to developing methodologies for predicting the carcinogenicity of chemicals on the basis of the results of short-term assays and selecting highly predictive batteries of short-term tests, a data base was assembled. The present is a compilation of data extracted from the reports of Gene-Tox working groups, Salmonella mutagenicity data obtained from the U.S. National Toxicology Program and the Environmental Mutagen Information Center and results from BHK21 transformation assays.     

Development of an in vitro test battery for the estimation of acute human systemic toxicity: An outline of the EDIT project. Evaluation-guided Development of New In Vitro Test Batteries

The aim of the Evaluation-guided Development of new In Vitro Test Batteries (EDIT) multicentre programme is to establish and validate in vitro tests relevant to toxicokinetics and for organ-specific toxicity, to be incorporated into optimal test batteries for the estimation of human acute systemic toxicity. The scientific basis of EDIT is the good prediction of human acute toxicity obtained with three human cell line tests (R(2) = 0.77), in the Multicentre Evaluation of In Vitro Cytotoxicity (MEIC) programme. However, the results from the MEIC study indicated that at least two other types of in vitro test ought to be added to the existing test battery to improve the prediction of human acute systemic toxicity - to determine key kinetic events (such as biotransformation and passage through biological barriers), and to predict crucial organ-specific mechanisms not covered by the tests in the MEIC battery. The EDIT programme will be a case-by-case project, but the establishment and validation of new tests will be carried through by a common, step-wise procedure. The Scientific Committee of the EDIT programme defines the need for a specific set of toxicity or toxicokinetic data. Laboratories are then invited to perform the defined tests in order to provide the "missing" data for the EDIT reference chemicals. The results obtained will be evaluated against the MEMO (the MEIC Monograph programme) database, i.e. against human acute systemic lethal and toxicity data. The aim of the round-table discussions at the 19th Scandinavian Society for Cell Toxicology (SSCT) workshop, held in Ringsted, Denmark on 6-9 September 2001, was to identify which tests are the most important for inclusion in the MEIC battery, i.e. which types of tests the EDIT programme should focus on. It was proposed that it is important to include in vitro methods for various kinetic events, such as biotransformation, absorption in the gut, passage across the blood-brain barrier, distribution volumes, protein binding, and renal clearance/accumulation. Models for target organ toxicity were also discussed. Because several of the outlier chemicals (paracetamol, digoxin, malathion, nicotine, paraquat, atropine and potassium cyanide) in the MEIC in vivo-in vitro evaluation have a neurotoxic potential, it was proposed that the development within the EDIT target organ programme should initially be focused on the nervous system.     

Screening for possible human carcinogens and mutagens. False positives, false negatives: statistical implications

A screening method aimed at identifying potential human carcinogens using either animal cancer bioassays or short-term genotoxic assays has 4 possible results: true positive, true negative, false positive and false negative. Such a categorisation is superficially similar to the results of hypothesis testing in a statistical analysis. In this latter case the false positive rate is determined by the significance level of the test and the false negative rate by the statistical power of the test. Although the two types of categorisation appear somewhat similar, different statistical issues are involved in their interpretation. Statistical methods appropriate for the analysis of the results of a series of assays include the use of Bayes' theorem and multivariate methods such as clustering techniques for the selection of batteries of short-term test capable of a better prediction of potential carcinogens. The conclusions drawn from such studies are dependent upon the estimates of values of sensitivity and specificity used, the choice of statistical method and the nature of the data set. The statistical issues resulting from the analysis of specific genotoxicity experiments involve the choice of suitable experimental designs and appropriate analyses together with the relationship of statistical significance to biological importance. The purpose of statistical analysis should increasingly be to estimate and explore effects rather than for formal hypothesis testing.     

Efficiency of the prediction of carcinogenic activities of chemical substances based on scoring somatic mutations in the soybean <Emphasis Type="Italic">Glycine max</Emphasis> (L.) Merrill

The efficiency of scoring somatic mutations in soybean (Glycine max (L.) Merrill) leaves as a test for carcinogenic activity of chemical substances in rodents has been evaluated. The efficiency of the test used alone or as part of a battery of tests has been estimated. The mutagenic activities of some chemical substances estimated using the soybean test are presented. Selective information on the carcinogenic activities of substances obtained in special carcinogenicity tests has been used as a quantitative measure of the efficiency of the tests with soybean leaves. To estimate the weight of evidence for the presence of this activity in the tested substances, a special function has been used whose values are uniquely related to the complete information, which is the sum of a priori information and the information obtained after testing. In general, the results have shown that the somatic mutation score test using soybean leaves is at least as efficient as the well-known tests that are generally used now, such as the Ames test and the chromosome aberration score test using mammalian cells in vitro. This test may be promising for the formation of efficient short-term test batteries.     

MEIC—A new international multicenter project to evaluate the relevance to human toxicity of in vitro cytotoxicity tests

A new international project to evaluate the relevance for human systemic and local toxicity of in vitro tests of general toxicity of chemicals has been organized by the Scandinavian Society of Cell Toxicology under the title Multicenter Evaluation of In Vitro Cytotoxicity (MEIC). The basic assumptions underlying the project, as well as the practical goals and the design of the program are outlined. The list of the first 50 reference chemicals is presented. The chemicals are an otherwise unbiased selection of compounds with known human acutely lethal dosage and blood concentrations, including LD50-values in the rat or mouse. Most agents also have other data on human toxicity and toxicokinetics, including more extensive animal toxicity data. International laboratories already using or developing in vitro tests of various partial aspects of general toxicity are invited to test the substances, the results of which will be evaluated by us. The predictivity of the in vitro results for both partial and gross human toxicity data will be determined with combined use of univariate regression analysis and soft multivariate modeling. The predictivity of the in vitro results will be compared with the predictivity of conventional animal tests for the same chemicals. Finally, batteries of tests with optimal prediction power for various types of human toxicity will be selected. The need for and possible uses of such batteries are discussed.     

Defining "adverse environmental impact" and making paragraph 316(b) decisions: a fisheries management approach

The electric utility industry has developed an approach for decisionmaking that includes a definition of Adverse Environmental Impact (AEI) and an implementation process. The definition of AEI is based on lessons from fishery management science and analysis of the statutory term "adverse environmental impact" and is consistent with current natural resource management policy. The industry has proposed a definition focusing on "unacceptable risk to the population"s ability to sustain itself, to support reasonably anticipated commercial or recreational harvests, or to perform its normal ecological function." This definition focuses not on counting individual fish or eggs cropped by the various uses of a water body, but on preserving populations of aquatic organisms and their functions in the aquatic community. The definition recognizes that assessment of AEI should be site-specific and requires both a biological decision and a balancing of diverse societal values. The industry believes that the definition of AEI should be implemented in a process that will maximize the overall societal benefit of the paragraph 316(b) decision by considering the facility"s physical location, design, and operation, as well as the local biology. The approach considers effects on affected fish and shellfish populations and the benefits of any necessary best technology available (BTA) alternatives. This is accomplished through consideration of population impacts, which conversely allows consideration of the benefits of any necessary BTA modifications. This in turn allows selection of BTAs that will protect potentially affected populations in a cost-effective manner. The process also employs risk assessment with stakeholder participation, in accordance with EPA's Guidelines for Ecological Risk Assessment. The information and tools are now available to make informed decisions about site-specific impacts that will ensure protection of aquatic ecosystems and best serve the public interest.     

Preparation and characterization of thick-film Ni/MH battery

Using the porous polypropylene (PP) films sputtered with gold and the Ni as current collectors, the electroactive materials (Ni(OH)2 and metal hydride (MH)) of positive and negative electrodes were prepared on the current collector using thick-film technology. Two types of cell configurations were prepared and the characteristics of these batteries were compared. The cycle number for the formation of batteries based on the porous PP film was found to be 2, which was significantly less than that of batteries based on the ceramic substrates. Using the porous PP film as substrate, the number of cycles for the formation of battery increased from 2 to 5 with the increase of the charge/discharge rate from 0.1C/0.025C to 2.0C/0.5C. The silver oxides dendrites formed by the oxidation of silver paste used to adhere the current collectors and the conducting wires in the charge/discharge process caused a short contact between the positive and negative electrodes, which then caused the battery failure. The cycle life of the battery based on the porous PP film was found to be greater than 400 when the charge/discharge rate was 2.0C/0.5C.     

Modelling the Impact and Cost-Effectiveness of Biomarker Tests as Compared with Pathogen-Specific Diagnostics in the Management of Undifferentiated Fever in Remote Tropical Settings

Background

Malaria accounts for a small fraction of febrile cases in increasingly large areas of the malaria endemic world. Point-of-care tests to improve the management of non-malarial fevers appropriate for primary care are few, consisting of either diagnostic tests for specific pathogens or testing for biomarkers of host response that indicate whether antibiotics might be required. The impact and cost-effectiveness of these approaches are relatively unexplored and methods to do so are not well-developed.

Methods

We model the ability of dengue and scrub typhus rapid tests to inform antibiotic treatment, as compared with testing for elevated C-Reactive Protein (CRP), a biomarker of host-inflammation. Using data on causes of fever in rural Laos, we estimate the proportion of outpatients that would be correctly classified as requiring an antibiotic and the likely cost-effectiveness of the approaches.

Results

Use of either pathogen-specific test slightly increased the proportion of patients correctly classified as requiring antibiotics. CRP testing was consistently superior to the pathogen-specific tests, despite heterogeneity in causes of fever. All testing strategies are likely to result in higher average costs, but only the scrub typhus and CRP tests are likely to be cost-effective when considering direct health benefits, with median cost per disability adjusted life year averted of approximately $48 USD and $94 USD, respectively.

Conclusions

Testing for viral infections is unlikely to be cost-effective when considering only direct health benefits to patients. Testing for prevalent bacterial pathogens can be cost-effective, having the benefit of informing not only whether treatment is required, but also as to the most appropriate antibiotic; this advantage, however, varies widely in response to heterogeneity in causes of fever. Testing for biomarkers of host inflammation is likely to be consistently cost-effective despite high heterogeneity, and can also offer substantial reductions in over-use of antimicrobials in viral infections.