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PubMed2002

The case definition of chronic fatigue syndrome.

The 1994 case definition of chronic fatigue syndrome is widely used not only for diagnosis but also for clinical and laboratory-based observations of this clinical entity. The criteria for the 1994 case definition are based primarily on symptoms and not on physical signs or chemical or immunological tests. This situation has resulted in conflicting clinical and laboratory observations that in all likelihood is due to different populations of patients being studied in different centers. Based on some of the recent publications, there appears to be an emerging picture of this disease entity that we propose could be used to subgroup chronic fatigue syndrome into four different subclasses. These subclasses would consist of chronic fatigue with primarily nervous system disorders such as impaired memory or concentration and headache, chronic fatigue with primarily endocrine system disorders such as unrefreshing sleep and postexertional malaise, chronic fatigue with musculoskeletal system disorders such as muscle pain and joint pain, and chronic fatigue with immune system/infectious disorders such as sore throat and tender lymph nodes. It is suggested that if clinical and laboratory-based studies on chronic fatigue syndrome were conducted on more homogeneous subgroups of patients, the data from one center to the other might not be as conflicting and more insights can be shed on the nature of this clinical condition.

Endocrine Glands↗

PubMed2005

Assessing case definitions in the absence of a diagnostic gold standard.

Optimal case definition is important in epidemiological research, but can be problematic when no satisfactory gold standard is available. In particular, difficulties arise where the pathology underlying a disorder is unknown or cannot be reliably diagnosed. This problem can be overcome if diagnoses are viewed not necessarily as labels for disease processes, but more generally as a useful method for classifying people for the purpose of preventing or managing illness. With this perspective, the value of a case definition lies in its practical utility in distinguishing groups of people whose illnesses share the same causes or determinants of outcome (including response to treatment). A corollary is that the best-case definition for a disorder may vary according to the purpose for which it is being applied.

Diagnosis↗

PubMed1995

Difficulties in clinical diagnosis of measles: proposal for modified clinical case definition.

OBJECTIVE: To examine the accuracy of clinical diagnosis of measles and to develop an improved measles clinical case definition. DESIGN: Case survey. SETTING: Eastern Sydney, December 1990 to August 1993. SUBJECTS: All cases of measles notified to the Eastern Sydney Public Health Unit without or before serological confirmation. OUTCOME MEASURES: Demographic and clinical details, measles- and rubella-specific IgM and measles complement fixation titres in acute and convalescent (when available) sera and epidemiological links with confirmed measles cases. RESULTS: Of 49 subjects reported and with complete follow-up, 24 were confirmed with measles, four with rubella and 21 had no definite diagnosis. Clinical diagnosis of measles had a false positive rate of 51%. Subjects with confirmed measles were significantly more likely to have a cough (23/24) than those with no definite diagnosis (15/21; P = 0.03) and to be febrile on the day of rash onset (23/24 versus 10/21; P = 0.001). The Centers for Disease Control definition had a sensitivity of 92% but specificity of only 24%. A modified case definition of rash, cough and fever present at onset of rash had equal sensitivity but greater specificity (57%). CONCLUSIONS: As measles is no longer common in Australia, clinical diagnosis is unreliable. When a public health response is needed, cases should be confirmed by serological tests or, if not available, we propose use of our modified clinical case definition.

Adolescent↗

PubMed2005

Clinical case definitions and malaria vaccine efficacy.

Reported efficacies from vaccine trials may depend heavily on the clinical case definition used in the trial. The dependence may be particularly striking for diseases such as malaria, in which no single case definition is appropriate. We used logistic regression modeling of the relationship between parasitemia and fever in data sets from Ghanaian children to determine the fraction of fevers attributable to malaria and to model how the choice of a threshold parasitemia in the clinical case definition affects the measured efficacy of malaria vaccines. Calculated clinical attack rates varied 10-fold as a function of the threshold parasitemia. Strikingly, measured vaccine efficacies in reducing clinical malaria depended heavily on the threshold parasitemia, varying between 20% and 80% as the threshold varied between 1 and 5000 parasites/ microL. We suggest that clinical case definitions of malaria that incorporate a threshold parasitemia are arbitrary and do not yield stable estimates of vaccine trial end points.

Animals↗

PubMed1997

Impact of the 1994 expanded World Health Organization AIDS case definition on AIDS surveillance in university hospitals and tuberculosis centers in Côte d'Ivoire.

OBJECTIVE: To assess the impact of the 1994 expanded World Health Organization (WHO) AIDS case definition on AIDS surveillance in Côte d'Ivoire. DESIGN: Prospective AIDS case surveillance. METHODS: From March 1994 through December 1996, passive AIDS case surveillance was conducted at the three university hospitals in Abidjan, and active AIDS case surveillance was conducted at the eight tuberculosis (TB) centers in Côte d'Ivoire. Standardized questionnaires were administered and blood samples for HIV serologic testing were collected from the patients evaluated. The numbers of persons who met the modified 1985 WHO clinical AIDS case definition (Bangui definition) and the 1994 expanded WHO AIDS case definition were determined, and the clinical characteristics of these patients were assessed. RESULTS: Of 8648 university hospital patients, 3658 (42.3%) met the clinical and/or the expanded case definition: 744 (20.3%) HIV-seropositive persons met only the expanded definition, 44 (1.2%) HIV-seropositive persons met only the clinical definition, 2334 (63.8%) HIV-seropositive persons met both definitions, and 536 (14.7%) HIV-seronegative persons met only the clinical definition. Of 18,661 TB center patients, 9664 (51.8%) met the clinical and/or the expanded definition: 5685 (58.8%) HIV-seropositive persons met only the expanded definition, none of the HIV-seropositive persons met only the clinical definition (by definition), 2625 (27.2%) HIV-seropositive persons met both definitions, and 1354 (14.0%) HIV-seronegative persons met only the clinical definition. CONCLUSIONS: Because of the inclusion of multiple severe HIV-related illnesses into the expanded definition, the number of reportable AIDS cases in HIV-seropositive patients increased 31.3% in the university hospitals, and 217% in the TB centers. The inclusion of HIV seropositivity as a criterion for the expanded definition also enhanced the specificity of AIDS case reporting, eliminating 536 cases in the university hospitals and 1354 cases in the TB centers in HIV-seronegative patients who had clinical signs of AIDS. The use of the 1994 expanded definition for surveillance purposes should be encouraged in areas of the developing world where HIV serologic testing is available.

AIDS-Related Opportunistic Infections↗

PubMed2002

The Brighton Collaboration: addressing the need for standardized case definitions of adverse events following immunization (AEFI).

UNLABELLED: To further scientific progress of immunization safety, comparability of data from clinical trials and surveillance systems is essential. Comparability requires the availability of standardized case definitions for adverse events following immunization (AEFI) and guidelines for case determination, recording and data presentation. METHOD: International collaborative working groups, consisting of professional volunteers from developed and developing countries, conduct systematic literature reviews to develop 50-100 AEFI definitions. Case definitions are finalized after a comment period by a reference group consisting of organizations concerned with immunization safety, and will be disseminated via the world-wide-web and other means for free world-wide use. RESULTS: Literature reviews yielded substantial diversity in data collection and presentation. We have developed standardized case definitions together with guidelines for use in clinical trials and surveillance systems. CONCLUSIONS: Diversity in safety methods leads to considerable loss of scientific information. We have built the necessary international network of currently about 300 participants from patient care, public health, scientific, pharmaceutical, regulatory and professional organizations to develop and assess standardized AEFI case definitions and guidelines. Evaluation studies, global implementation, ongoing definition development and a continuously growing network will be essential for the success of the collaboration.

Adverse Drug Reaction Reporting Systems↗

PubMed2006

Public health implications of using various case definitions in The Netherlands during the worldwide SARS outbreak.

This study analysed the consequences of deviation from the WHO case definition for the assessment of patients with suspected severe acute respiratory syndrome (SARS) in The Netherlands during 2003. Between 17 March and 7 July 2003, as a result of dilemmas in balancing sensitivity and specificity, five different case definitions were used. The patients referred for SARS assessment were analysed from a public health perspective. None of the patients referred had SARS, based on serological and virological criteria. Nevertheless, all 72 patients required thorough assessment and, depending on the results of the assessment, institution of appropriate prevention and control measures. Changing case definitions caused confusion in classifying cases. A centralised assessment of the reported cases by a team with clinical and public health expertise (epidemiological and geographical risk assessment) is a practical solution for addressing differences in applying case definitions. The burden of managing non-cases is an important issue when allocating public health resources, and should be taken into account during the preparation phase, rather than during an outbreak. This applies not only to SARS, but also to other public health threats, such as pandemic influenza or a bioterrorist episode.

Antibodies, Viral↗

PubMed2006

Performance of the Brighton collaboration case definition for hypotonic-hyporesponsive episode (HHE) on reported collapse reactions following infant vaccinations in the Netherlands.

We reviewed collapse (sudden onset of pallor, limpness and hyporesponsiveness) following the first infant (DPTP+Hib) vaccination reported to the enhanced passive surveillance system of the Netherlands in 1994-2003. All 1303 reports identified by the current RIVM (National Institute for Public Health and Environment) case definition were captured by the Brighton Collaboration (BC) case definition, with in 17 (1.3%) reports insufficient information. Over the years the proportion of the highest level of diagnostic certainty (level 1) increased due to more complete data from 70% to over 90%. We checked the BC case definition also on a sample of cases (with pallor or hyporesponsiveness) not meeting RIVM's case definition for collapse at the time. Sixty out of 200 cases were captured by BC but again rejected by RIVM. The sensitivity BC levels 2 and 3 appeared too high. We recommend a more restrict case definition by the Brighton Collaboration with certain exclusion criteria to make it more specific. Furthermore a change in the specifications for levels 2 and 3 will increase specificity and accommodate for the loss of sensitivity.

Age Factors↗

PubMed2003

Heterogeneous case definitions used for the surveillance of influenza in Europe.

We reviewed the case definitions used by 21 influenza sentinel-based surveillance networks in Western Europe. Two clinical syndromes were used with a wide range of case definitions that nevertheless shared common criteria. Although there is currently no international consensus, efforts are being undertaken to standardise influenza case definitions in Europe.

Diagnosis, Differential↗

PubMed2006

Diagnosing smear-negative tuberculosis using case definitions and treatment response in HIV-infected adults.

OBJECTIVE: To assess the diagnostic utility of expanded case definitions for HIV-associated smear-negative pulmonary tuberculosis (PTB) and extra-pulmonary TB (EPTB), and to derive objective criteria for response to anti-tuberculosis treatment. DESIGN: A prospective cohort study of HIV-infected adults who met expanded clinical case definitions for smear-negative PTB and EPTB. METHODS: All participants were started on rifampicin-based anti-tuberculosis treatment after mycobacterial cultures from multiple sites. At weeks 2, 4 and 8, response to treatment (RTT) was assessed by measuring changes in weight, haemoglobin, C-reactive protein, Karnofsky performance score and symptom count ratio. RESULTS: Of 147 participants enrolled, 105 (71%) were diagnosed with definite (culture-positive) or probable (histological features) TB and 25 (17%) with possible TB (treatment response). The positive predictive value for the most common case definitions ranged from 89% to 96%. Significant improvements in all the RTT parameters occurred in the subjects with confirmed TB (P < 0.001). Clinically relevant RTT criteria were derived, two or more of which were met at week 8 in 97.5% of subjects with confirmed TB, 91.3% of subjects with possible TB and none of the subjects without TB. CONCLUSION: Expanded case definitions could enhance the diagnosis of PTB and EPTB in HIV-infected adults in resource-limited settings. Using objective criteria, RTT can be assessed within 8 weeks of initiating anti-tuberculosis treatment.

AIDS-Related Opportunistic Infections↗

PubMed2005

Evaluation of the Brighton Collaboration case definition of acute intussusception during active surveillance.

To evaluate the Brighton Collaboration case definition of acute intussusception, we reviewed all episodes reported to the Swiss Paediatric Surveillance Unit (SPSU) during 1 year (4/2003--3/2004). Of 96 confirmed episodes 86 (90%, 95% CI 83--96) were captured by the case definition. Of the remaining 10 episodes, 9 resolved spontaneously following presentation with clinical signs and symptoms, and ultrasound findings compatible with intussusception. Eighty-two episodes met level 1 of the definition, the highest level of diagnostic certainty. Compared to level 1, the sensitivity of level 2 (intermediate level) and level 3 (lowest level) was 65% (CI 55--74) and 30% (CI 20--40), respectively. In conclusion, the case definition was useful and applicable to assess the background rate of intussusception in the light of potential future rotavirus immunization.

Child, Preschool↗

PubMed1996

European Union Concerted Action on Risk Assessment in Lyme Borreliosis: clinical case definitions for Lyme borreliosis.

The EU Concerted Action on Risk Assessment in Lyme Borreliosis (EUCALB) has consulted other clinicians and scientists in Europe to produce case definitions of the principal manifestations of European Lyme borreliosis. These case definitions will not only be helpful in supporting its own research interests, but are also intended to assist other clinicians in appropriate management and to support further studies aimed at determining the full clinical spectrum of the disease. The case definitions were achieved after a series of meetings organised by EUCALB with other expert clinicians and scientists from twelve European countries. The definitions and the diagnostic criteria presented thus represent the consensus reached at these meetings. The proposed case definitions consider skin, nervous system, cardiac and musculoskeletal presentations and the role of laboratory investigation in supporting diagnosis.

Acrodermatitis↗

PubMed2006

The effect of altitude on parasite density case definitions for malaria in northeastern Tanzania.

OBJECTIVES: Malaria clinical trials need precise endpoints to measure efficacy. In endemic areas where asymptomatic parasitaemia is common, 'fever plus parasitaemia' may not differentiate between malaria cases and non-cases. Case definitions based on parasite cut-off densities may be more appropriate but may vary with age and transmission intensity. This study examines appropriate case definitions from parasitological surveys conducted over a broad range of transmission intensities, using altitude as a proxy for transmission intensity. METHODS: Cross-sectional data collected from 24 villages at different altitudes in an endemic area of northeastern Tanzania were used to calculate malaria-attributable fractions using a modified Poisson regression method. We modelled fever as a function of parasite density and determined the optimum cut-off densities of parasites to cause fever using sensitivity and specificity analyses. RESULTS: The optimum cut-off density varied by altitude in children aged under 5 years: a case definition of 4,000 parasites per mul at altitudes <600 m (high transmission intensity) was most appropriate, compared with 1,000 parasites per mul at altitudes >600 m (low transmission intensity). In children aged over 5 years and adults, there was little variation by altitude and a case definition of any parasites plus fever was the most appropriate. CONCLUSIONS: Locally appropriate case definitions of malaria should be used for research purposes. In our setting, these varied independently with age and transmission intensity.

Adolescent↗

PubMed1991

Acellular pertussis vaccines. Efficacy and evaluation of clinical case definitions.

The efficacy of two acellular pertussis vaccines was estimated for various clinical case definitions, with and without the requirement of culture confirmation, from a randomized trial in Sweden. Efficacy increased with duration of coughing spasms and when the case definition included whoops or whoops plus at least nine coughing spasms a day. After deletion of clinical cases not believed to be caused by pertussis, efficacies were closer to the higher values for culture-confirmed disease. Nonspecificity of the clinical criterion "21 days of coughing spasms with whoops" resulted in estimates of predictive value for pertussis of 85% for placebo recipients and 56% for vaccinees. We conclude that laboratory confirmation of suspected cases is needed in pertussis vaccine trials. A suggested case definition is 21 days or more of coughing spasms with confirmation by culture, serologic study, or household exposure to culture-confirmed pertussis.

Humans↗

PubMed1987

Evaluation of a clinical case definition of AIDS in African children.

In July 1986, a provisional clinical case definition of AIDS in children, developed by the World Health Organization (WHO) for surveillance purposes in Africa, was tested on 159 patients hospitalized in the Department of Pediatrics at Mama Yemo Hospital, Kinshasa, Zaire. Twenty-one (13%) of these children were seropositive for HIV. In this population, the clinical case definition of pediatric AIDS was found to be fairly specific (87%) but lacked sensitivity (35%). The positive predictive value for HIV seropositivity was 25%. This study suggests that it is more difficult to define AIDS clinically in children than in adults and that the utility of the proposed WHO clinical case definition for pediatric AIDS for surveillance of children's AIDS in Africa is limited.

Acquired Immunodeficiency Syndrome↗

PubMed2002

Development of case definitions for acute encephalopathy, encephalitis, and multiple sclerosis reports to the vaccine: Adverse Event Reporting System.

The Vaccine Adverse Event Reporting System (VAERS), administered by the FDA and CDC, is the U.S. system for surveillance of vaccine adverse events (AE). Acute encephalopathy age <18 months (EO < 18), age > or =18 months (EO > or = 18), encephalitis (EI), and multiple sclerosis (MS) after vaccination have been reported to VAERS, but reports often contain insufficient information to validate diagnoses. Standardized case definitions would enhance the utility of VAERS reports for AE surveillance. We developed practical case definitions for classification of VAERS reports, and three neurologists independently applied the definitions to reports submitted in 1993. Inter-observer agreement was assessed, and non-concordant classifications were reviewed in a follow-up conference call. Reports of EO < 18 (n = 8), EO > or = 18 (n = 20), EI (n = 15), and MS (n = 16) were classified as "definite" in 7% to 30% of the cases, while 26% to 51% of reports were thought to have insufficient information to make a classification. Agreement among reviewers was good to excellent, (kappa: 0.65 to 0.85) except for EO < 18 m for which it was marginal (kappa: 0.37). It is possible to develop reproducible case definitions for acute encephalopathy, encephalitis, and multiple sclerosis using a standardized approach. Application of standardized case definitions to VAERS reports documents the limited information in many reports, specifies data for supplemental collection, and indicates that VAERS reports should be cautiously interpreted. Development and application of case definitions for other adverse events reported after vaccination should enhance the value of vaccine safety databases. Published by Elsevier Science Inc.

Acute Disease↗

PubMed2006

Heterogeneity of case definitions used in vaccine effectiveness studies--and its impact on meta-analysis.

In the literature, different definitions of clinical illness cases and observation period are used to assess influenza vaccine effectiveness, usually without addressing their actual specificity and sensitivity. These properties, however, have large implications on influenza vaccine effectiveness estimates in single trials and meta-analyses of trials. Re-arranging 30 trials (in 17 publications) with a total of 29,265 subjects according to specificity and sensitivity of their case definitions and observation periods, resulted in large differences between vaccine effectiveness estimates for various levels of specificity and sensitivity. For highly specific definitions the combined vaccine effectiveness estimate was 54%, but for highly sensible definitions only 11%. Such findings call for a cautious interpretation of combined vaccine effectiveness estimates. Internationally agreed case and observation period definitions would be desirable to facilitate future meta-analyses.

Humans↗

PubMed2004

Recent trends in infective endocarditis: influence of case definitions.

PURPOSE OF REVIEW: Infective endocarditis continues to pose major challenges in diagnosis and management despite advances in understanding the epidemiology, microbiology, and pathology of the disease. The purpose of this article is to provide a review of diagnosis, microbiology, and treatment of infective endocarditis, particularly as they are influenced by case definitions. RECENT FINDINGS: Case definitions have a critical effect on the interpretation of trends in infective endocarditis, and recent studies have proposed more specific criteria. Studies have also addressed the appropriate use of echocardiography to assist in the diagnosis and management of infective endocarditis. Staphylococcus aureus has become an increasingly common cause of infective endocarditis, and the microbiology of nosocomial infective endocarditis is changing. Newer techniques are being used to aid in the identification of causal agents in blood culture-negative infective endocarditis. Antimicrobial guidelines for the treatment of infective endocarditis are readily available, including a proposal to avoid premature discharge of patients on outpatient antibiotic therapy. Additional studies have been conducted on combination antibiotic therapy, duration of treatment, dosing of aminoglycosides, alternative agents for gram-positive organisms, aspirin therapy, and surgical interventions. SUMMARY: Recent trends in diagnosis, microbiology, and treatment of infective endocarditis are described, and case definitions play a critical role in their interpretation.

Anti-Bacterial Agents↗