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PubMed1991

Validation of a surveillance case definition of carpal tunnel syndrome.

The National Institute for Occupational Safety and Health (NIOSH) has proposed a surveillance case definition for work-related carpal tunnel syndrome (CTS). The case definition requires the presence of median nerve symptoms; one or more occupational risk factors; and objective evidence of CTS including one of three physical examination findings or nerve conduction tests diagnostic of CTS. We evaluated the performance of the NIOSH case definition, restricting our analysis to cases in which physical examination findings served as the objective criterion. Nerve conduction studies were used as the gold standard. Seventy-eight workers were studied; 38 percent had CTS. The NIOSH case definition had sensitivity of 0.67 (95% CI = 0.57, 0.77), specificity of 0.58 (95% CI = 0.47, 0.69), and positive and negative predictive values of 0.50 (95% CI = 0.39, 0.61) and 0.74 (95% CI = 0.64, 0.84), respectively. Overall 38 percent of subjects were classified incorrectly. In a sample with a prevalence of 15 percent, as might be encountered in high risk workplaces, the positive predictive value would be 0.22. In conclusion, when physical examination findings serve as the objective criterion the performance of the case definition is modest reflecting the limited diagnostic value of its component tests and indicating that effective screening for CTS awaits improved diagnostic techniques.

Adult↗

PubMed2006

Performance of rubella suspect case definition: implications for surveillance.

OBJECTIVE: To assess the performance of the rubella suspect case definition among patients with rash diseases seen at primary care units. METHODS: From January 1994 to December 2002, patients with acute rash, with or without fever, were seen at two large primary health care units and at a public general hospital in the municipality of Niterói, metropolitan area of Rio de Janeiro, Brazil. Data from clinical and serologic assessment were used to estimate the positive predictive values of the definition of rubella suspect case from the Brazilian Ministry of Health and other combination of signs/symptoms taking serologic status as the reference. Serum samples were tested for anti-rubella virus IgM using commercially available enzyme immunoassays. Positive predictive values and respective 95% confidence intervals were calculated. RESULTS: A total of 1,186 patients with an illness characterized by variable combinations of rash with fever, arthropathy and lymphadenopathy were studied. Patients with rash, regardless of other signs and symptoms, had 8.8% likelihood of being IgM-positive for rubella. The Brazilian suspect case definition (fever and lymphadenopathy in addition to rash) had low predictive value (13.5%). This case definition would correctly identify 42.3% of the IgM-positive cases, and misclassify 26.1% of the IgM-negative cases. CONCLUSIONS: These results support the recommendation to investigate and collect clinical specimens for laboratory diagnosis of all cases of rash, for surveillance purposes. Although this strategy may increase costs, the benefits of interrupting the circulation of rubella virus and preventing the occurrence of congenital rubella syndrome should pay off.

Antibodies, Viral↗

PubMed1995

Natural history of benign prostatic hyperplasia: appropriate case definition and estimation of its prevalence in the community.

There is no consensus about a case definition of benign prostatic hyperplasia (BPH). In the present study, BPH prevalence rates were determined using various case definitions based on a combination of clinical parameters used to describe the properties of BPH: symptoms of prostatism, prostate volume increase, and bladder outflow obstruction. The aim of this study--in a community-based population of 502 men (55-74 years of age) without prostate cancer--was to determine the relative impact on prevalence rates of the inclusion of these different parameters (and of different cutoff values for these parameters) in a case definition of BPH. There is agreement that age is the dominant determinant of BPH. However, of 28 different case definitions that were formulated, only eight gave a statistically significant increase in the prevalence of BPH with age. The highest overall prevalence of 19% (95% confidence interval [CI], 15-23%) occurred using the definition that combines a prostate volume > 30 cm3 and an International Prostate Symptom Score (IPSS) > 7. The lowest prevalence rate of 4.3% (95% CI, 2-6%) occurred using the definition that combines a prostate volume > 30 cm3, an IPSS > 7, a maximum flow rate < 10 mL/s, and the presence of a postvoid residual urine volume > 50 mL. Thus, prevalence rates depend very much on the parameters used in a case definition. Follow-up will establish which men will eventually request a workup and treatment for BPH and will help determine the best clinical definition of BPH.

Age Factors↗

PubMed1988

Potential effect of revising the CDC surveillance case definition for AIDS.

The Centers for Disease Control (CDC) revised the surveillance case definition for acquired immunodeficiency syndrome (AIDS) in August, 1987. To determine the impact of this revision, information was extracted from the medical charts of the 630 patients receiving comprehensive medical care as of 1980 at 6 haemophilia treatment centres, and who were therefore likely to have been infected with human immunodeficiency virus (HIV). 38 (6%) and 47 (7%) met the 1985 and 1987 case definitions, respectively (22% increase). Of the cases added by use of the 1987 case definition, 3 patients had HIV dementia, 3 had Pneumocystis carinii pneumonia (2 of whom were presumptively diagnosed and 1 who had been receiving steroids and immunosuppressives), and 3 had HIV wasting syndrome. These data suggest that the revision of the AIDS case definition will have a substantial impact on future AIDS surveillance trends in persons with haemophilia and perhaps in other risk groups.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Tuberculosis surveillance in the United States: case definitions used by state health departments.

Health departments in all 53 reporting areas in the United States were asked to submit the case definition they used for tuberculosis surveillance. Sixteen areas used the 1990 case definition; two areas sent 1977 guidelines; and 34 areas sent other definitions. Case reports sent to the Centers for Disease Control and Prevention (CDC) in 1992 were analyzed; 4% of cases did not meet the 1990 definition. Tuberculosis case reporting criteria are not uniformly applied in the United States. CDC, in collaboration with state and local health officials, is evaluating the current definition and will implement uniform national criteria for tuberculosis surveillance.

Adolescent↗

PubMed2004

[On the 2004 edition of case definitions for the surveillance of notifiable infectious diseases in Germany].

With the beginning of the year 2004, new case definitions of the Robert Koch Institute (RKI) replace those introduced in 2001. The new edition provides definitions for 53 categories of cases that are to be reported by local health departments through state health authorities to the RKI according to the German infectious disease control act. The new case definitions take into account recent developments in laboratory methods and indications for improvement identified through systematic evaluation. The case definitions consist of three types of evidence-clinical picture, laboratory detection, and epidemiological confirmation-all of which list disease- or pathogen-specific test criteria. Combining the three evidence types results in five case definition categories: clinically diagnosed illness, clinically and epidemiologically confirmed illness, clinically and laboratory-confirmed illness, laboratory-detected infection not fulfilling clinical criteria, and laboratory-detected infection with unknown clinical picture.

Communicable Disease Control↗

PubMed2004

Influence of clinical case definitions with differing levels of sensitivity and specificity on estimates of the relative and absolute health benefits of influenza vaccination among healthy working adults and implications for economic analyses.

Clinical illness case definitions for influenza and methods used to define influenza seasons can vary substantially from study to study. These differences often result in differing levels of sensitivity, specificity and positive predictive value for the case definitions used. We explored the implications of different case definitions and outcome periods on estimates of influenza vaccine effectiveness and cost benefit by conducting additional analyses of data collected from a randomized, double blind, placebo controlled trial of the trivalent, intranasal, live attenuated influenza virus vaccine in healthy working adults. Febrile upper respiratory tract illnesses occurring during the peak influenza period was identified as the most specific clinical case definition expected to have the highest positive predictive value for true influenza whereas events occurring on a day with any symptom occurring during the entire outcome period was identified as the most sensitive clinical case definition with the lowest positive predictive value for influenza. As expected, the former provided the highest estimates of vaccine effectiveness (28.4% reduction in work loss days, 24.6% reduction in days with impaired productivity and 40.9% reduction in days with health care provider visits) but the lowest estimates of absolute reductions in events (42.4 work loss days prevented per 1000, 79.0 impaired productivity days per 1000, and 16.5 days with health care provider visits per 1000). On the other hand, events on days with any symptom during the entire outcome period provided the lowest estimates of vaccine effectiveness (18% reduction in work loss days, 18% reduction in days with impaired productivity, and 13% reduction in days with health care provider visits) but the highest estimates of absolute reductions in events (186.4 work loss days per 1000, 271.5 impaired productivity days per 1000, and 44.8 days with health care provider visits per 1000). When applied to a cost benefit analysis, the more specific case definition provided a break even cost for vaccination of US$ 6.58 whereas the more sensitive case definition provided a break even cost for vaccination of US$ 43.07. Clearly the latter combination is most appropriate when trying to assess the total population level impact of a vaccine preventable disease and the potential cost effectiveness of vaccination whereas the former may be most appropriate for assessing whether the vaccine actually works. The definitions of clinical influenza illness and outcome periods should be selected to match the study question.

Adult↗

PubMed2005

Validation of a surveillance case definition for arthritis.

OBJECTIVE: To assess whether self-reports of chronic joint symptoms or doctor-diagnosed arthritis can validly identify persons with clinically verifiable arthritis. METHODS: The Behavioral Risk Factor Surveillance System (BRFSS), a telephone health survey, defines a case of arthritis as a self-report of chronic joint symptoms (CJS) and/or doctor-diagnosed arthritis (DDx). A sample of health plan enrollees aged 45-64 years and >/= 65 years with upcoming annual physical examinations were surveyed by telephone using the 2002 BRFSS CJS and DDx questions. Based on responses (CJS+, DDx-; CJS-, DDx+; CJS+, DDx+; CJS-, DDx-), respondents were recruited to undergo a standardized clinical history and physical examination for arthritis (the gold standard for clinical validation). Weighted sensitivities and specificities of the case definition were calculated to adjust for sampling. RESULTS: Of 2180 persons completing the telephone questionnaire, 389 were examined; of these, 258 met the case definition and 131 did not. For those examined and aged 45 to 64 years (n = 179), 96 persons had arthritis confirmed, of whom 76 met the case definition. Among those examined and aged >/= 65 (n = 210), 150 had arthritis confirmed, of whom 124 met the case definition. Among those without clinical arthritis, 45 of 83 of those aged 45 to 64 years and 40 of 60 of those aged >/= 65 did not meet the case definition. For those aged 45 to 64 years, the weighted sensitivity of the case definition in this sample was 77.4% and the weighted specificity was 58.8%; for those aged >/= 65, the sensitivity was 83.6% and specificity 70.6%. CJS+ had higher sensitivity and lower specificity than DDx+ in the younger age group; CJS+ and DDx+ behaved more comparably in the older age group. CONCLUSION: The case definition based on self-reported CJS and/or DDx appeared to be sensitive in identifying arthritis, but specificity was lower than desirable for those under age 65 years. Better methods of ascertaining arthritis by self-report are needed. Until then, a change in the surveillance case definition for arthritis appears warranted.

Aged↗

PubMed2004

Clinical case definition for the diagnosis of acute intussusception.

OBJECTIVE: Because of the reported association between intussusception and a rotavirus vaccine, future clinical trials of rotavirus vaccines will need to include intussusception surveillance in the evaluation of vaccine safety. The aim of this study is to develop and validate a clinical case definition for the diagnosis of acute intussusception. METHODS: A clinical case definition for the diagnosis of acute intussusception was developed by analysis of an extensive literature review that defined the clinical presentation of intussusception in 70 developed and developing countries. The clinical case definition was then assessed for sensitivity and specificity using a retrospective chart review of hospital admissions. Sensitivity of the clinical case definition was assessed in children diagnosed with intussusception over a 6.5-year period. Specificity was assessed in patients aged <2 years admitted with bowel obstruction and in patients aged <19 years presenting with symptoms that may occur in intussusception. RESULTS: The clinical case definition accurately identified 185 of 191 assessable cases as "probable" intussusception and six cases as "possible" intussusception (sensitivity, 97%). No case of radiologic or surgically proven intussusception failed to be identified by the clinical case definition. The specificity of the definition in correctly identifying patients who did not have intussusception ranged from 87% to 91%. CONCLUSIONS: The clinical case definition for intussusception may assist in the prompt identification of patients with intussusception and may provide an important tool for the future trials of enteric vaccines.

Acute Disease↗

PubMed1998

Surveillance case definitions for work related upper limb pain syndromes.

OBJECTIVES: To establish consensus case definitions for several common work related upper limb pain syndromes for use in surveillance or studies of the aetiology of these conditions. METHODS: A group of healthcare professionals from the disciplines interested in the prevention and management of upper limb disorders were recruited for a Delphi exercise. A questionnaire was used to establish case definitions from the participants, followed by a consensus conference involving the core group of 29 people. The draft conclusions were recirculated for review. RESULTS: Consensus case definitions were agreed for carpal tunnel syndrome, tenosynovitis of the wrist, de Quervain's disease of the wrist, epicondylitis, shoulder capsulitis (frozen shoulder), and shoulder tendonitis. The consensus group also identified a condition defined as "non-specific diffuse forearm pain" although this is essentially a diagnosis made by exclusion. The group did not have enough experience of the thoracic outlet syndrome to make recommendations. CONCLUSIONS: There was enough consensus between several health professionals from different disciplines to establish case definitions suitable for use in the studies of several work related upper limb pain syndromes. The use of these criteria should allow comparability between studies and centres and facilitate research in this field. The criteria may also be useful in surveillance programmes and as aids to case management.

Arm↗

PubMed2003

Variations in case definition affect prevalence but not outcomes of mild cognitive impairment.

OBJECTIVE: To examine the prevalence estimates and 5-year outcomes of various case definitions of mild cognitive impairment (MCI). METHODS: The authors examined 1,790 adults 65 years of age or older who completed neuropsychological and clinical assessments in the Canadian Study of Health and Aging, a 5-year, representative, prospective cohort study. RESULTS: The most commonly used case definition of MCI yielded a population prevalence estimate of 1.03% (95% CI 0.66 to 1.40). Eliminating the requirements for subjective memory complaints and intact instrumental activities of daily living (IADL) increased the prevalence to 3.02% (CI 2.40 to 3.64). Five-year outcomes, including the risk of death, institutionalization, and dementia, were not distinctly different for various case definitions of MCI, but all were at increased risk of institutionalization (RR 2.3 to 5.2) and dementia (RR 9.3 to 19.7). Regardless of the case definition, most people with MCI developed dementia, chiefly Alzheimer disease (AD). Still, for each case definition, almost one third were considered to have no cognitive impairment after 5 years. CONCLUSIONS: Memory complaints and intact IADL may be unnecessary requirements for a case definition of MCI in population-based samples. The MCI criteria identify people at increased risk of AD, but the potential for improvement of a substantial proportion of those with MCI needs to be acknowledged.

Aged↗

PubMed2000

Epidemiological case definitions of peripheral neuropathy: experience from two neurotoxicity studies.

OBJECTIVE: The purpose of this investigation was to develop and apply case definitions of peripheral neuropathy (PN) derived from a set of individual measures of peripheral nerve function obtained in two epidemiological studies. METHODS: In the first study, retired workers of an industrial plant who were either previously exposed to mercury or not underwent a set of peripheral neurological tests. In the second study, persons living in an arsenic contaminated community in rural Georgia, USA, and unexposed comparison subjects were tested. In both studies all participants received a neurological physical examination, functional quantitative tests of vibrotactile thresholds and standing stability, and nerve conduction measurements. Two types of analyses were performed. First, the effect of exposure group status was examined for each individual test. For tests with continuous outcomes, the effect of exposure group was estimated while controlling for covariates. For tests with categorical outcomes (all of the neurological examination outcomes), exposure group effects were estimated by comparison of the proportion of abnormal test results among the exposed and unexposed groups. Second, case definitions of PN were constructed using combinations of results of the tests performed. Each of the continuous measures was categorized as normal, equivocal, or abnormal on the basis of adjusted standardized scores. Separate "abnormality scores" were constructed for 1) the nerve conduction tests and 2) the functional quantitative tests and physical examination findings. Five case definitions for PN were constructed based on combinations of these two abnormality scores. RESULTS: Generally, small differences were observed between exposed (n=79 arsenic exposed and 85 mercury exposed) and unexposed (n=84 arsenic unexposed and 118 mercury unexposed) groups when results of each clinical, functional or electrophysiological test were examined separately. Clearer group differences were observed in the proportions of each group who met case definitions for PN, however. For example, for both studies, the largest difference in nerve conduction measures between exposed and unexposed groups was approximately 0.33 SD, while the composite case definition showed an odds ratio of more than 3.1 for the mercury study and 5.1 for the arsenic study. CONCLUSIONS: These results suggest improved efficiency (and avoidance of the multiple-comparisons problem) for detecting peripheral nerve effects when case definitions of PN are constructed rather when results of individual tests of PN function are compared.

Adult↗

PubMed1999

The impact of the 1993 AIDS case definition on the completeness and timeliness of AIDS surveillance.

OBJECTIVE: To assess the impact of the 1993 change in the AIDS case definition on the completeness and timeframe of AIDS case reporting in San Francisco. DESIGN: Retrospective review of records: billing records, list of selected diagnostic codes, radiology logs, ophthalmology clinic records, and patient registries at a selection of hospitals, clinics, and physician offices. SETTING: Hospitals, public/community health clinics, and physician offices. MAIN OUTCOME MEASURES: The completeness of reporting and the median reporting delay was calculated for hospitals, clinics, and physician offices. RESULTS: Reporting was 97% complete. Reporting from physician offices was less complete (75%) than from other facilities. The median reporting delay was 1 month and was shorter for persons who met the 1993 AIDS case definition (1 month) than for persons who met the 1987 case definition (3 months). CONCLUSIONS: AIDS case reporting in San Francisco is highly complete but less so for persons diagnosed at physician offices. The 1993 AIDS case definition has resulted in more timely reporting. Health departments should consider efforts to improve reporting from private physician offices and should evaluate the use of laboratory-initiated CD4 reporting.

Acquired Immunodeficiency Syndrome↗

PubMed2006

Heterogeneity of influenza case definitions and implications for interpreting and comparing study results.

There is substantial heterogeneity with regard to influenza case definitions used in the medical literature. These different case definitions can vary substantially with regard to their sensitivity, specificity and positive and negative predictive values for confirmed influenza. Because of this heterogeneity, it is important that the appropriate case definitions be used to answer the specific questions of the study, with more specific definitions likely being used to answer questions of vaccine efficacy and more sensitive definitions being used to assess overall disease burden. When interpreting the results of studies and comparing results across studies it is essential that the issue of heterogeneity of case definitions be addressed, and that absolute risk reduction be used as the main outcome measure of interest rather than just the relative risk reduction.

Humans↗

PubMed1990

Effect of the revised AIDS case definition on AIDS reporting in San Francisco: evidence of increased reporting in intravenous drug users.

To examine the effect of the revision of the US national AIDS case definition in September 1987, we compared demographic and clinical information for AIDS patients diagnosed and reported to the San Francisco Department of Public Health between 1 September 1987 and 31 October 1989. Of the 3167 patients diagnosed and reported during the study period, 584 (18%) met the revised case definition only, increasing AIDS case reporting in San Francisco by 23%. One hundred and thirty-four of these 584 patients (23%) subsequently developed diagnoses meeting the old definition. After adjusting for this proportion, the revised case definition increased reporting by 17%. The mean time between initial diagnosis with a disease meeting the revised definition and subsequent development of a disease meeting the old definition was 18.5 months. Patients who met the revised case definition only were slightly older and more likely to be Black, female, and intravenous drug users (IVDUs) than those meeting the old case definition. The majority of patients who met the revised case definition only had initial diagnoses of HIV wasting syndrome (26%), HIV encephalopathy (21%), and presumptive Pneumocystis carinii pneumonia (19%). The revised AIDS case definition has significantly increased the reporting of severe morbidity associated with HIV infection, particularly among IVDUs.

AIDS Dementia Complex↗

PubMed2005

Outcomes of incident mild cognitive impairment in relation to case definition.

Definitions of mild cognitive impairment (MCI) vary, yielding conflicting results. For example, case definitions affect prevalence but not outcomes in prevalent cases. Our objective was to determine whether variation in case definitions affects outcomes in incident cases of MCI. The 5 year risks of death, institutionalisation, and dementia were evaluated in clinically examined incident MCI cases in the Canadian Study of Health and Aging. The definition of MCI was varied so as to include or relax combinations of diagnostic features from consensus criteria. Relative risks (RR) of each adverse outcome were highest in MCI case definitions that required subjective memory complaints (for example, RR of dementia = 26.4-38.7). Although each MCI definition conferred an increased risk of dementia, for each case definition 20-30% of survivors had no cognitive impairment at follow up. In this population based study, MCI represented a transitional state, but was heterogeneous, with substantial proportions recovering, regardless of how MCI was defined. Factors associated with recovery and non-progression in MCI require elucidation.

Activities of Daily Living↗

PubMed2003

HIV lipodystrophy case definition using artificial neural network modelling.

OBJECTIVE: A case definition of HIV lipodystrophy has recently been developed from a combination of clinical, metabolic and imaging/body composition variables using logistic regression methods. We aimed to evaluate whether artificial neural networks could improve the diagnostic accuracy. METHODS: The database of the case-control Lipodystrophy Case Definition Study was split into 504 subjects (265 with and 239 without lipodystrophy) used for training and 284 independent subjects (152 with and 132 without lipodystrophy) used for validation. Back-propagation neural networks with one or two middle layers were trained and validated. Results were compared against logistic regression models using the same information. RESULTS: Neural networks using clinical variables only (41 items) achieved consistently superior performance than logistic regression in terms of specificity, overall accuracy and area under the ROC curve. Their average sensitivity and specificity were 72.4 and 71.2%, as compared with 73.0 and 62.9% for logistic regression, respectively (area under the ROC curve, 0.784 vs 0.748). The discriminating performance of the neural networks was largely unaffected when built excluding 13 parameters that patients may not have readily available. The average sensitivity and specificity of the neural networks remained the same when metabolic variables were also considered (total 60 items) without a clear advantage against logistic regression (overall accuracy 71.8%). The performance of networks considering also body composition variables was similar to that of logistic regression (overall accuracy 78.5% for both). CONCLUSIONS: Neural networks may offer a means to improve the discriminating performance for HIV lipodystrophy, when only clinical data are available and a rapid approximate diagnostic decision is needed. In this context, information on metabolic parameters is apparently not helpful in improving the diagnosis of HIV lipodystrophy, unless imaging and body composition studies are also obtained.

Absorptiometry, Photon↗

PubMed2005

Survival of AIDS patients using two case definitions, Rio de Janeiro, Brazil, 1986-2003.

BACKGROUND: Recent studies have shown substantial increases in the survival of AIDS patients in developed countries and in Brazil as a result of antiretroviral therapy (ART) and prophylaxis for opportunistic infections. This study compares survival rates using the Brazilian Ministry of Health 2004 and Centers for Disease Control and Prevention (CDC) 1993 case definitions in a large HIV/AIDS referral centre in Rio de Janeiro. METHODS: Survival after AIDS diagnosis was assessed in a clinic-based cohort of 1415 individuals using the Kaplan-Meier method and Cox proportional hazards models. RESULTS: There were 393 (88%) deaths from AIDS-related causes and 52 (12%) from unrelated or unknown causes. A total of 205 patients (14%) were lost to follow-up and 765 patients (55%) remained alive until the end of the study. Three-quarters of patients (75%) were still alive 22 months [95% confidence interval (CI) 19-26] after the AIDS diagnosis according to the CDC case definition and 31 months (95% CI 26-36) according to the Ministry of Health case definition. Independent predictors of survival included AIDS defined by CD4 cell count and any use of highly active antiretroviral therapy, with either case definition, and initial stage of the case, with the Ministry of Health case definition. CONCLUSION: Survival observed in this reference centre is comparable or longer than other international studies, although the choice of case definition criterion influenced findings. Adoption of the Ministry of Health case definition may enhance the ability to track the use of and outcomes from ART among AIDS patients.

Acquired Immunodeficiency Syndrome↗