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PubMed1997

Case definitions.

The definition of a case of pertussis is an essential point in evaluating and comparing the results from the seven studies on pertussis vaccines presented at the Symposium. An assessment of the impact of case definition on the evaluation of vaccine efficacy has been performed on the Italian data-set, by comparing the clinical presentation of cough illnesses which were laboratory-confirmed as B. pertussis infection with those not-confirmed, by study vaccine. The results show that the estimate of vaccine efficacy is greatly variable by the choice of case definition and dependent on the study design. The assessment of the effect of each vaccine should be performed by using various clinical endpoints and the method used in detection of suspected cases in each study should be carefully evaluated to verify comparability of results.

Cough↗
PubMed2006

Reliability of case definitions for public health surveillance assessed by Round-Robin test methodology.

BACKGROUND: Case definitions have been recognized to be important elements of public health surveillance systems. They are to assure comparability and consistency of surveillance data and have crucial impact on the sensitivity and the positive predictive value of a surveillance system. The reliability of case definitions has rarely been investigated systematically. METHODS: We conducted a Round-Robin test by asking all 425 local health departments (LHD) and the 16 state health departments (SHD) in Germany to classify a selection of 68 case examples using case definitions. By multivariate analysis we investigated factors linked to classification agreement with a gold standard, which was defined by an expert panel. RESULTS: A total of 7870 classifications were done by 396 LHD (93%) and all SHD. Reporting sensitivity was 90.0%, positive predictive value 76.6%. Polio case examples had the lowest reporting precision, salmonellosis case examples the highest (OR = 0.008; CI: 0.005-0.013). Case definitions with a check-list format of clinical criteria resulted in higher reporting precision than case definitions with a narrative description (OR = 3.08; CI: 2.47-3.83). Reporting precision was higher among SHD compared to LHD (OR = 1.52; CI: 1.14-2.02). CONCLUSION: Our findings led to a systematic revision of the German case definitions and build the basis for general recommendations for the creation of case definitions. These include, among others, that testable yes/no criteria in a check-list format is likely to improve reliability, and that software used for data transmission should be designed in strict accordance with the case definitions. The findings of this study are largely applicable to case definitions in many other countries or international networks as they share the same structural and editorial characteristics of the case definitions evaluated in this study before their revision.

Attitude of Health Personnel↗
PubMed2003

Revised U.S. surveillance case definition for severe acute respiratory syndrome (SARS) and update on SARS cases--United States and worldwide, December 2003.

During the 2003 epidemic of severe acute respiratory syndrome (SARS), CDC and the Council of State and Territorial Epidemiologists (CSTE) developed surveillance criteria to identify persons with SARS. The surveillance case definition changed throughout the epidemic as understanding of the clinical, laboratory, and transmission characteristics of SARS-associated coronavirus (SARS-CoV) increased. On June 26, CSTE adopted a position statement to add SARS-CoV disease to the National Notifiable Disease Surveillance System (NNDSS). The position statement included criteria for defining a SARS case for national reporting. On November 3, CSTE issued a new interim position statement with a revised SARS case definition. This report summarizes the new U.S. surveillance case definition for SARS and updates reported cases of SARS worldwide and in the United States.

Disease Outbreaks↗
PubMed1993

Expanded AIDS case definition increases Pennsylvania's reported AIDS cases.

At the beginning of 1993, the Centers for Disease Control and Prevention adopted an expanded case definition of AIDS and a revision of the classification system for HIV infection for persons ages 13 years or older. This article explains the changes and their effects, defines the new system categories, and offers resources for physicians treating HIV-infected patients.

AIDS-Related Opportunistic Infections↗
PubMed2003

Rethinking the boundaries of Kawasaki disease: toward a revised case definition.

This paper describes the historical evolution of the Kawasaki disease (KD) case definition and its limitations for identification and treatment of children at risk for coronary artery aneurysms (CAA). The dominant view of pathogenesis is that an unknown agent infects infants and children, who then develop the signs of KD. Some of the infected infants and children then develop CAA, and a few die from myocardial infarction. Because the etiologic agent remains unknown, diagnosis of KD relies on observation and recognition of the clinical signs that comprise the KD case definition criteria. This approach has been successful in identifying and treating many children at risk for CAA. Unfortunately, however, it has delayed the effective treatment of children who fail to meet the KD case definition criteria but who, nevertheless, develop CAA. The original case definition was developed before the general acceptance of CAA as sequelae of KD, the availability of the echocardiogram, and effective treatment with intravenous immunoglobulin. Despite an evolution in awareness, detection, and treatment of possible CAA sequela, the case definition has not been altered so as to incorporate this knowledge. Our investigation explores the transformation of the case definition from an epidemiological instrument to a diagnostic tool. We urge the construction of a more sensitive KD case definition that includes signs and laboratory findings associated with CAA.

Child↗
PubMed1993

Impact of the 1993 revision of the AIDS case definition on the prevalence of AIDS in a clinical setting.

OBJECTIVE: To determine the impact of the 1993 revision of the Centers for Disease Control and Prevention (CDC) AIDS surveillance case definition on the prevalence of AIDS. DESIGN: Review of prospectively collected baseline clinical and demographic data on HIV-infected patients presenting for care between December 1988 and May 1991. SETTING: The HIV Clinic of the Johns Hopkins Hospital, an urban, primary care institution. MAIN OUTCOME MEASURE: Diagnosis of AIDS by the 1987 (specific indicator diseases) or the 1993 (indicator diseases, pulmonary tuberculosis, recurrent bacterial pneumonia, cervical carcinoma, or CD4 lymphocyte count < 200 x 10(6)/l) CDC case definition. RESULTS: Of 955 patients evaluated, 122 (13%) had AIDS by the 1987 case definition at presentation. An additional 126 (13%) met the 1993 but not the 1987 case definition. Patients meeting only the 1993 case definition were more likely to be female [28 versus 14%; odds ratio (OR), 2.4; 95% confidence interval (CI), 1.2-3.0; P = 0.01] and intravenous drug users (40 versus 26%; OR, 2.0; 95% CI, 1.1-3.3; P = 0.02) than patients meeting the 1987 case definition. Fifty-five per cent of patients meeting only the 1993 case definition were asymptomatic, and 7% (nine patients) had new indicator diseases but CD4 counts > 200 x 10(6)/l. Median time to progression from a diagnosis of AIDS by the 1993 case definition to diagnosis by the 1987 case definition was 435 days. Patients with AIDS by the 1987 case definition had a median survival of 594 days from presentation (2-year survival, 42%), while median survival time for patients with AIDS by the 1993 case definition only was 947 days (2-year survival, 60%; P < 0.005). CONCLUSIONS: The proposed 1993 revision of the AIDS surveillance case definition would double the number of prevalent AIDS cases, with significant increases in the proportion of cases who are female, intravenous drug users, or asymptomatic. Survival of patients meeting the 1993 case definition is significantly longer than that of patients meeting the 1987 case definition. The new AIDS case definition will have a major impact both on AIDS surveillance and on medical and social service programs that use diagnosis of AIDS as a criterion for eligibility for services.

AIDS-Related Opportunistic Infections↗
PubMed1994

A comparison of case definitions of chronic fatigue syndrome.

We compared three case definitions of chronic fatigue syndrome (CFS) applied to patients followed in CFS clinics at two institutions. All patients had debilitating fatigue without apparent etiology; patients with medical conditions associated with chronic fatigue and with major psychiatric disorders were stratified and presented separately. Patients were classified according to whether they met case definitions developed by a Centers for Disease Control and Prevention (CDC) Working Group, a British group, or an Australian group. When findings for 805 patients followed at the two clinics were combined, 61% met the CDC criteria, 55% met the British criteria, and 56% met the Australian criteria; these proportions were relatively similar at both sites. In addition, similar laboratory abnormalities were found for all case groups and for fatigued patients who met none of the three case definitions. These data suggest that more inclusive case definitions may be superior.

Adult↗
PubMed1988

Evaluation of the WHO clinical case definition for AIDS in rural Zaire.

The clinical case definition for AIDS proposed by WHO for use in Africa was evaluated against HIV antibody status in 72 patients in rural Zaire. Twenty-one (29%) of the patients were antibody-positive. For diagnosing anti-HIV seropositivity, the case definition had a sensitivity of 52%, a specificity of 78%, a positive predictive value of 50% and a negative predictive value of 80%. Calculation of the positive predictive value at different levels of prevalence of HIV infection suggests that the case definition operates at maximum reliability in selected high-risk groups. Modifications to the case definition should be evaluated to try and improve its sensitivity and positive predictive value.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Human immunodeficiency virus disease in California. Effects of the 1993 expanded case definition of the acquired immunodeficiency syndrome.

On January 1, 1993, the case definition of the acquired immunodeficiency syndrome (AIDS) in adults and adolescents used for monitoring the AIDS epidemic in California was expanded to include persons infected with the human immunodeficiency virus (HIV) with CD4 T-lymphocyte counts of less than 200 x 10(6) per liter (< 200 per mm3), pulmonary tuberculosis, recurrent pneumonia, or invasive cervical cancer. To assess the implications of this revision on AIDS case reporting in California, we compared cases reported through the end of 1994 based on 1 or more of the 4 new AIDS-defining conditions added in 1993 to cases reported based on pre-1993 AIDS-defining opportunistic infections and cancers. The 4 new conditions included in the 1993 expanded AIDS case definition accounted for a 23% increase in cumulative AIDS cases reported in California by the end of 1993, a 170% increase in the number of cases reported during 1993, and an 88% increase in the number of patients with AIDS living at the end of 1993. The number of cases reported in 1993 (19,629) was 124% more than that reported in 1992 (8,780) and 69% more than that reported in 1994 (11,587). The proportion of cases among women, injection-drug users, and African Americans also increased as a result of this change in the case definition. The expansion of the case definition may have resulted in a peak or plateau in the AIDS incidence in California because of reporting earlier in the HIV disease progression. The expanded case definition has enhanced the usefulness of AIDS surveillance data for targeting secondary prevention efforts, but more behavioral and HIV serosurveys are still needed to adequately target primary HIV prevention efforts.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Evaluation of the measles clinical case definition.

An accurate system of identifying and classifying suspected measles cases is critical for the measles surveillance system in the United States. To examine the performance of the clinical case definition in predicting laboratory confirmation of suspected cases of measles, we reviewed 4 studies conducted between 1981 and 1994. A clinical case definition was examined that included a generalized maculopapular rash, fever (>or=38.3 degrees C, if measured), and either a cough, coryza, or conjunctivitis. Serological confirmation of measles was done either by hemagglutination inhibition assay, complement fixation assay, or enzyme immunoassays. The positive predictive value of the clinical case definition decreased from 74% to 1% as incidence decreased from 171 cases/100000 population to 1.3 cases/100000 population. Sensitivity was high, and for the larger studies with the most precise estimates, sensitivity was 76%-88%. The low positive predictive value of the clinical case definition in settings of low incidence demonstrates that serological confirmation is essential to ensure an accurate diagnosis of measles when measles is rare.

Adolescent↗
PubMed2006

[On the 2007 edition of case definitions for the surveillance of notifiable infectious diseases in Germany].

The revised case definitions established by the Robert Koch Institute will become effective on 1 January 2007. The case definitions provide criteria for the reporting of mandatory notifiable infectious diseases according to the German infectious disease control act. The new case definitions take into account recent developments in laboratory methods. Furthermore in the new edition the criteria were updated and clarified if necessary. For each case definition a paragraph 'reference definition' is introduced and explained. If applicable additional information (e.g., vaccination history) to be reported was added. In this article, the major changes of the revised case definitions are described.

Communicable Disease Control↗
PubMed1992

Impact of the 1987 revised AIDS case definition in Denmark: a follow-up study 2 years after its adoption.

We present a follow-up study on Danish AIDS patients notified according to the latest revision of the AIDS case definition during the first 2 years after its adoption. A total of 271 adult AIDS cases were notified in the period of study (Jan. 1, 1988-Dec. 31, 1989). 60 patients (22%) met only the revised AIDS case definition and of these 17 patients (28%) developed diseases meeting the old AIDS case definition. Thus, AIDS reporting increased by 28% due to the change in case definition, the impact being 19% after adjusting for patients developing old case diseases. No time trend in the impact was found. We estimated the cumulative percent of cases meeting the new case definition who subsequently will develop diseases meeting the old definition as 15% after 6 months and 51% after 18 months. The revision produced a disproportionate increase in reporting of female cases (p less than 0.05), transfusion cases (p less than 0.01) and to a lesser extent of heterosexual cases, while the impact on reporting of homo/bisexual men showed a decrease (p less than 0.01). Cases notified with new case definition diseases were older than cases notified with old diseases. Among patients meeting only the new case definition, 25 died and 18 (30%) had not developed old case diseases before death. We found no difference in survival rates between patients within the 2 groups of case definition. Among patients meeting the new definition we found no differences in HIV antigenemia or CD4 cell count between those developing diseases meeting old case definition and those who did not.

Acquired Immunodeficiency Syndrome↗
PubMed1996

An examination of the working case definition of chronic fatigue syndrome.

PURPOSE: Chronic fatigue syndrome (CFS) currently is defined by a working case definition developed under the leadership of the United States Centers for Disease Control and Prevention (CDC) based on a consensus among experienced clinicians. We analyzed the experience from one large center to examine the adequacy of the case definition. PATIENTS AND METHODS: Predefined clinical and laboratory data were collected prospectively from 369 patients with debilitating fatigue, of whom 281 (76%) met the major criteria of the original CDC case definition for CFS: (1) fatigue of at least 6 months' duration, seriously interfering with the patient's life; and (2) without evidence of various organic or psychiatric illnesses that can produce chronic fatigue. The same clinical data were obtained from 311 healthy control subjects and two comparison groups with diseases that can present in a similar fashion; relapsing-remitting multiple sclerosis (n = 25) and major depression (n = 19). RESULTS: All of the minor criteria symptoms from the original CDC case definition distinguished patients with debilitating chronic fatigue from healthy control subjects, and many distinguished the patients with chronic fatigue from the comparison groups with multiple sclerosis and depression: myalgias, postexertional malaise, headaches, and a group of infectious-type symptoms (ie, chronic fever and chills, sore throat, swollen glands in the neck or underarm areas). In addition, two other symptoms not currently part of the case definition discriminated the chronic fatigue patients from the control/comparison groups: anorexia and nausea. Physical examination criteria only infrequently contributed to the diagnosis. Patients meeting the CDC major criteria for CFS also met the minor criteria in 91% of cases. CONCLUSION: Patients meeting the major criteria of the current CDC working case definition of CFS reported symptoms that were clearly distinguishable from the experience of healthy control subjects and from disease comparison groups with multiple sclerosis and depression. Eliminating three symptoms (ie, muscle weakness, arthralgias, and sleep disturbance) and adding two others (ie, anorexia and nausea) would appear to strengthen the CDC case definition of CFS.

Adult↗
PubMed2005

Development of a validated clinical case definition of generalized tonic-clonic seizures for use by community-based health care providers.

PURPOSE: To develop and test a clinical case definition for identification of generalized tonic-clonic seizures (GTCSs) by community-based health care providers. METHODS: To identify symptoms that can help identify GTCSs, patients with history of a jerky movements or rigidity in any part of the body ever in life were recruited from three sites: the community, secondary care hospital, and tertiary care hospital. These patients were administered a 14-item structured interview schedule focusing on the circumstances surrounding the seizure. Subsequently, a neurologist examined each patient and, based on available investigations, classified them as GTCS or non-GTCS cases. A logistic regression analysis was performed to select symptoms that were to be used for case definition of GTCSs. Validity parameters for the case definition at different cutoff points were calculated in another set of subjects. RESULTS: In total, 339 patients were enrolled in the first phase of the study. The tertiary care hospital contributed the maximal number of GTCS cases, whereas cases of non-GTCS were mainly from the community. At the end of phase I, the questionnaire was shortened from 14 to eight questions based on statistical association and clinical judgment. After phase II, which was conducted among 170 subjects, three variables were found to be significantly related to the presence of GTCSs by logistic regression: absence of stress (13.1; 4.1-41.3), presence of frothing (13.7; 4.0-47.3), and occurrence in sleep (8.3; 2.0-34.9). As a case definition using only three variables did not provide sufficient specificity, three more variables were added based on univariate analysis of the data (incontinence during the episode and unconsciousness) and review of literature (injury during episode). A case definition consisting of giving one point to an affirmative answer for each of the six questions was tested. At a cutoff point of four, sensitivity was 56.9 (47.4-66.0) and specificity, 96.3 (86.2-99.4). Among the 197 GTCS and 26 new non-GTCS patients recruited from hospitals from select SEAR Member Countries, in phase III, the sensitivity of this clinical case definition was 72% and specificity, 100%. A stratified analysis by gender in all the three phases did not show any differences between the sexes. CONCLUSIONS: Based on these criteria, we recommend that all patients with a history of two or more episodes of jerking or rigidity of limbs, having a score of > or =4 in the case definition, be identified as having GTCSs and started on antiepileptic medications. This clinical case definition can be very useful for community-based health care providers to identify and manage cases of GTCSs in the community. This should play a major role in the reduction of treatment gap for epilepsy in developing countries.

Adolescent↗
PubMed2005

Case definitions of clinical malaria under different transmission conditions in Kilifi District, Kenya.

BACKGROUND: Clear case definitions of malaria are an essential means of evaluating the effectiveness of present and proposed interventions in malaria. The clinical signs of malaria are nonspecific, and parasitemia accompanied by a fever may not be sufficient to define an episode of clinical malaria in endemic areas. We defined and quantified cases of malaria in people of different age groups from 2 areas with different rates of transmission of malaria. METHODS: A total of 1602 people were followed up weekly for 2 years, and all the cases of fever accompanied by parasitemia were identified. Logistic regression methods were used to derive case definitions of malaria. RESULTS: Two case definitions of malaria were derived: 1 for children 1-14 years old and 1 for infants (<1 year old) and older children and adults (> or =15 years old). We also found a higher number of episodes of clinical malaria per person per year in people from an area of low transmission of malaria, compared with the number of episodes in those from an area of higher transmission (0.84 vs. 0.55 episodes/person/year; incidence rate ratio, 0.66 [95% confidence interval, 0.61-0.72]; P<.001). CONCLUSIONS: Case definitions of malaria are bound to be altered by factors that affect immunity, such as age and transmission. Case definitions may, however, be affected by other immunity-altering factors, such as HIV and vaccination status, and this needs to be borne in mind during vaccine trials.

Adolescent↗
PubMed1998

The impact of the 1993 European revision of the AIDS case definition on back-calculation estimates: an application in Italy.

OBJECTIVES: The revision of the case definition for AIDS within a given observation period causes discontinuity points on the epidemic curve to which back-calculation procedures can be sensitive. The aim of this work is to characterize the impact of the 1993 European revision of AIDS case definition and to evaluate the degree of distortion by which back-calculation estimates obtained on Italian data are affected. METHODS: The back-calculation procedure used, is a generalization of standard methods for estimating and projecting the AIDS epidemic. Age at onset of HIV infection, incubation time distribution, susceptible population and competitive non-AIDS mortality rates for infected persons are included in the estimation process. RESULTS: Back-calculation estimates resulted to be sensitive to the discontinuity point that the 1993 revision of AIDS case definition induced on the epidemic curve. The resulting effect is a tendency to overestimate HIV incidence in recent years by 20-40%. The maximum effect was found using data with end of AIDS cases at December 1993. The overestimation is a transient effect, that is, it is expected to almost disappear in 1995-1996. CONCLUSIONS: The introduction of the 1993 European revision of AIDS case definition caused distortion of back-calculation estimates in Italy, leading to overestimate incidence and prevalence of HIV infection for recent years. It is believed that this effect has occurred in all countries that adopted the 1993 European revision of AIDS case definition, and its characterization is potentially useful for further changes of AIDS case definition in the future.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Diagnostic accuracy of three clinical case definitions for advanced HIV disease.

OBJECTIVE: To assess the accuracy of three clinical case definitions for advanced HIV disease: the World Health Organization (WHO) case definition, and the original and revised Caracas case definitions. DESIGN: Retrospective chart review. SETTING: A clinic for patients with all stages of HIV infection at the Johns Hopkins Hospital, Baltimore, [correction of Bethesda] Maryland, USA, a tertiary care university hospital. PATIENTS, PARTICIPANTS: Two hundred and twenty-four HIV-positive adults who underwent initial evaluation between 1 January 1990 and 31 December 1990. MAIN OUTCOME MEASURES: A score for each definition was assigned based on initial evaluation. The sensitivity, specificity, and predictive values were calculated using the Centers for Disease Control (CDC) staging criteria, and results were correlated with total CD4 cell counts. RESULTS: The sensitivities of the WHO, and the original and revised Caracas definitions were 40, 67, and 60%, respectively, using CDC disease stage IV as a positive standard. Specificities were between 99 and 100%, using CDC stage II-III disease as a negative standard. Mean CD4 cell counts for patients with positive scores were 184, 160, and 158 x 10(6)/l, respectively, compared to 191 x 10(6)/l for CDC stage IV patients. Sensitivity was lower when the positive standard was expanded to include all patients with CD4 cell counts less than 200 x 10(6)/l. CONCLUSIONS: In our study population, case definitions were specific, but only moderately sensitive for advanced HIV disease. Prospective studies should be conducted in diverse geographic regions, using lymphocyte or CD4 cell counts when possible.

Acquired Immunodeficiency Syndrome↗