[Odds ratio or prevalence ratio? Their use in cross-sectional studies].
ABSTRACT The most commonly used measures of association in cross-sectional studies are the odds ratio (OR) and the prevalence ratio (PR). Some cross-sectional epidemiologic studies describe their results as OR but use the definition of PR. The main aim of this study was to describe and compare different calculation methods for PR described in literature using two situations (prevalence < 20% and prevalence > 20%).
A literature search was carried out to determine the most commonly used techniques for estimating the PR. The four most frequent methods were: 1) obtaining the OR using non-conditional logistic regression but using the correct definition; 2) using Breslow-Cox regression; 3) using a generalized linear model with logarithmic transformation and binomial family, and 4) using the conversion formula from OR into PR. The models found were replicated for both situations (prevalence less than 20% and greater than 20%) using real data from the 1994 Catalan Health Interview Survey.
When prevalence was low, no substantial differences were observed in either the estimators or standard errors obtained using the four procedures. When prevalence was high, differences were found between estimators and confidence intervals although all the measures maintained statistical significance.
All the methods have advantages and disadvantages. Individual researchers should decide which technique is the most appropriate for their data and should be consistent when using an estimator and interpreting it.
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ABSTRACT: Obstructive lung disease (OLD) is frequently unrecognized and undertreated. Urban drug users are at higher risk for OLD due to race, behavioral, and socioeconomic characteristics, yet little data exist on prevalence and risk factors associated with unrecognized OLD in this population. The objective of this study is to determine the prevalence of unrecognized OLD in an urban population and identify the characteristics associated with lack of physician-diagnosed OLD. Cross-sectional analysis from the Acquired Immunodeficiency Syndrome Linked to the Intravenous Experience (ALIVE) study, an observational study of current and former injection drug users in Baltimore, Maryland, USA. All participants with spirometry-defined airflow obstruction were stratified by the presence or absence of physician diagnosis of OLD. Using cross-sectional demographic, clinical, and spirometric measurements, multivariable regression models were generated to identify factors independently associated with unrecognized OLD. Of the 1083 participants evaluated in the ALIVE lung substudy, 176 (16.3%) met spirometric criteria for OLD. Of those, only 88 (50%) had a physician diagnosis of OLD. The prevalence of unrecognized OLD decreased as severity of airflow obstruction increased. Factors independently associated with unrecognized OLD were absence of respiratory symptoms (prevalence ratio [PR], 1.70; 95% confidence interval [CI]: 1.29-2.23; P < 0.01) and less severe dyspnea (PR, 0.83; 95% CI: 0.72-0.96, per point increase in dyspnea scale; P = 0.01). In the subset of human immunodeficiency virus (HIV)-infected participants, the use of antiretroviral therapy (ART) was independently associated with an increased prevalence of unrecognized OLD (PR, 1.93; 95% CI: 1.05-3.56; P = 0.03). In a cohort of current and former urban drug users, OLD is substantially underrecognized and associated with lack of respiratory symptoms. Relying on the presence of respiratory symptoms as a trigger to perform spirometry may result in a substantial underdiagnosis of OLD in this population. HIV-infected individuals receiving ART are a population particularly vulnerable to unrecognized OLD.International Journal of COPD 01/2011; 6:89-95.
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ABSTRACT: Objective. To determine the prevalence of leptospirosis in patients from Veracruz with initial diagnosis of dengue and its association with risk factors. Materials and Methods. Transversal study in patients who sought medical attention under the suspicion of dengue. Backgrounds were researched and blood samples were drawn to determine dengue (NS1, RT-PCR) and leptospirosis (IFI). Simple frequencies, central tendency and dispersion measures, and prevalence and trust intervals at 95% (IC95%) were obtained. Prevalence reasons (RP) and IC(95%) were obtained and a multivariate logistic model was applied, using SPSS V15. Results. 171 patients were included, 56% women (32 ± 14 years) and 44% men (32 ± 17 years). 48% of the cases (IC95% 40.5-55.4) was positive to dengue, with a cut point of 1 : 80, seroprevalence for leptospirosis was of 6% (IC(95%) 2.7-10); 12% (IC95% 7-16.5) was positive to both pathologies and 34% was negative to both tests. Although the largest number of isolations corresponded to serotype 2, the four dengue virus serotypes were identified. In the bivariate analysis, overcrowding RP = 1.33, (IC = 0.46-3.5), bathing in rivers (RP = 1.31, IC = 0.13-7.4), and walking barefoot (RP = 1.39, IC = 0.58-3.3) were the variables associated with leptospirosis, although the relation was not statistically significant. Conclusions. Leptospirosis prevalence in subjects under suspicion of dengue fever is high, as well as the coincidence of both infections. The results show the coexistence of overlapped outbreaks of several diseases sharing the side of transmission. It is necessary the intentional search of other pathologies, such as influenza, rickettsiosis, and brucella, among others.Journal of Tropical Medicine 01/2012; 2012:519701.
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ABSTRACT: BACKGROUND: Aesthetic alterations in the face can be self-perceived and can affect quality of life. For young people, physical attractiveness is an important factor affecting social relationships. The aim of this study was to estimate the prevalence of malocclusion, identify the most common types and test its association with oral aesthetic self-perception in 18 to 21 year-old population of male young adults. METHODS: A cross-sectional study was carried out involving 138 Brazilian Army soldiers. Data collection included socio demographic profile, malocclusion status through the Dental Aesthetic Index (DAI) and oral aesthetic self-perception as indicated by the Oral Aesthetic Subjective Impact Scale (OASIS). The chi-square and Fisher's exact test were used to test for homogeneity of proportions. The stepwise multivariate logistic regression analysis was used to test for the relationship between the poorer oral aesthetic self-perception and parental and soldier's education, per capita income, history of caries in all teeth and only on anterior teeth, dental trauma, previous orthodontic treatment and malocclusion. RESULTS: The prevalence of malocclusion was 45.6%. Incisor teeth crowding and misalignment of lower incisors were the most common types of malocclusions. A statistically significant and independent association between malocclusion and poorer oral aesthetic self-perception in the multivariate analysis was observed. Subjects with severe malocclusion conditions showed 88% higher prevalence [prevalence ratio =1.88 (95% CI, 1.30 -- 2.72); p = 0.001] of poorer aesthetic self-perception comparing to those with minor malocclusion. CONCLUSIONS: A high prevalence of malocclusion was observed. The young adults presenting severe malocclusion had a higher and independent prevalence of poorer oral aesthetic self-perception.BMC Oral Health 01/2013; 13(1):3. · 1.34 Impact Factor