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ABSTRACT: BACKGROUND: Individual signs and symptoms are of limited value for the diagnosis of influenza. OBJECTIVE: To develop a decision tree for the diagnosis of influenza based on a classification and regression tree (CART) analysis. METHODS: Data from two previous similar cohort studies were assembled into a single dataset. The data were randomly divided into a development set (70%) and a validation set (30%). We used CART analysis to develop three models that maximize the number of patients who do not require diagnostic testing prior to treatment decisions. The validation set was used to evaluate overfitting of the model to the training set. RESULTS: Model 1 has seven terminal nodes based on temperature, the onset of symptoms and the presence of chills, cough and myalgia. Model 2 was a simpler tree with only two splits based on temperature and the presence of chills. Model 3 was developed with temperature as a dichotomous variable (≥38°C) and had only two splits based on the presence of fever and myalgia. The area under the receiver operating characteristic curves (AUROCC) for the development and validation sets, respectively, were 0.82 and 0.80 for Model 1, 0.75 and 0.76 for Model 2 and 0.76 and 0.77 for Model 3. Model 2 classified 67% of patients in the validation group into a high- or low-risk group compared with only 38% for Model 1 and 54% for Model 3. CONCLUSIONS: A simple decision tree (Model 2) classified two-thirds of patients as low or high risk and had an AUROCC of 0.76. After further validation in an independent population, this CART model could support clinical decision making regarding influenza, with low-risk patients requiring no further evaluation for influenza and high-risk patients being candidates for empiric symptomatic or drug therapy.
Family Practice 03/2012; · 1.50 Impact Factor
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ABSTRACT: A clinical decision rule to improve the accuracy of a diagnosis of influenza could help clinicians avoid unnecessary use of diagnostic tests and treatments. Our objective was to develop and validate a simple clinical decision rule for diagnosis of influenza.
We combined data from 2 studies of influenza diagnosis in adult outpatients with suspected influenza: one set in California and one in Switzerland. Patients in both studies underwent a structured history and physical examination and had a reference standard test for influenza (polymerase chain reaction or culture). We randomly divided the dataset into derivation and validation groups and then evaluated simple heuristics and decision rules from previous studies and 3 rules based on our own multivariate analysis. Cutpoints for stratification of risk groups in each model were determined using the derivation group before evaluating them in the validation group. For each decision rule, the positive predictive value and likelihood ratio for influenza in low-, moderate-, and high-risk groups, and the percentage of patients allocated to each risk group, were reported.
The simple heuristics (fever and cough; fever, cough, and acute onset) were helpful when positive but not when negative. The most useful and accurate clinical rule assigned 2 points for fever plus cough, 2 points for myalgias, and 1 point each for duration <48 hours and chills or sweats. The risk of influenza was 8% for 0 to 2 points, 30% for 3 points, and 59% for 4 to 6 points; the rule performed similarly in derivation and validation groups. Approximately two-thirds of patients fell into the low- or high-risk group and would not require further diagnostic testing.
A simple, valid clinical rule can be used to guide point-of-care testing and empiric therapy for patients with suspected influenza.
The Journal of the American Board of Family Medicine 01/2012; 25(1):55-62. · 2.05 Impact Factor
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ABSTRACT: The potential effects of increasing numbers of uninsured and underinsured persons on US emergency departments (EDs) is a concern for the health care safety net.
To describe the changes in ED visits that occurred from 1997 through 2007 in the adult and pediatric US populations by sociodemographic group, designation of safety-net ED, and trends in ambulatory care-sensitive conditions.
Publicly available ED visit data from the National Hospital Ambulatory Medical Care Survey (NHAMCS) from 1997 through 2007 were stratified by age, sex, race, ethnicity, insurance status, safety-net hospital classification, triage category, and disposition. Codes from the International Classification of Diseases, Ninth Revision (ICD-9), were used to extract visits related to ambulatory care-sensitive conditions. Visit rates were calculated using annual US Census estimates.
Total annual visits to US EDs and ED visit rates for population subgroups.
Between 1997 and 2007, ED visit rates increased from 352.8 to 390.5 per 1000 persons (rate difference, 37.7; 95% confidence interval [CI], -51.1 to 126.5; P = .001 for trend); the increase in total annual ED visits was almost double of what would be expected from population growth. Adults with Medicaid accounted for most of the increase in ED visits; the visit rate increased from 693.9 to 947.2 visits per 1000 enrollees between 1999 and 2007 (rate difference, 253.3; 95% CI, 41.1 to 465.5; P = .001 for trend). Although ED visit rates for adults with ambulatory care-sensitive conditions remained stable, ED visit rates among adults with Medicaid increased from 66.4 in 1999 to 83.9 in 2007 (rate difference, 17.5; 95% CI, -5.8 to 40.8; P = .007 for trend). The number of facilities qualifying as safety-net EDs increased from 1770 in 2000 to 2489 in 2007.
These findings indicate that ED visit rates have increased from 1997 to 2007 and that EDs are increasingly serving as the safety net for medically underserved patients, particularly adults with Medicaid.
JAMA The Journal of the American Medical Association 08/2010; 304(6):664-70. · 30.03 Impact Factor
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ABSTRACT: We seek to compare ultrasonographically guided peripheral intravenous access to a non-ultrasonographically guided method in a randomized trial of emergency department patients with difficult intravenous access.
A prospective cohort of patients with difficult intravenous access was established. Patients were randomized to 2 groups: (1) intravenous access obtained through an ultrasonographically guided technique or (2) intravenous access obtained through non-ultrasonographically guided methods. Outcomes measured were number of attempts after enrollment, time to cannulation from enrollment, and patient satisfaction. Groups were compared with nonparametric analysis.
Fifty-nine patients were randomized. Twenty-eight patients were randomized to the ultrasonography group and 31 to the no ultrasonography group. A median of 2 further intravenous attempts was required in each group before successful cannulation, corresponding to a difference of 0 attempts (95% confidence interval [CI] 0 to 1 attempts). Time to cannulation showed a median of 39 minutes in the ultrasonography group compared with 26 minutes for the no ultrasonography group, giving a median increase of 13 minutes for the ultrasonographically guided group (95% CI -5 to 28 minutes). Patients in the ultrasonography group had a median Likert satisfaction score of 8 compared with 7 for the no ultrasonography group, giving a median increase of 1 on this scale in the ultrasonography group (95% CI 0 to 2).
Ultrasonographically guided peripheral intravenous cannulation did not decrease the number of attempts or the time to successful catheterization, nor did it improve patient satisfaction compared with the group that did not use ultrasonography. Superiority of ultrasonographically guided peripheral intravenous cannulation is not supported by this study.
Annals of emergency medicine 10/2008; 54(1):33-40. · 4.23 Impact Factor
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ABSTRACT: The purpose of this study is to compare ultrasonographic visualization of the jugular and common femoral veins by using a novel technique (humming) and 2 conventional techniques (Valsalva's maneuver and Trendelenburg's position). The Valsalva's maneuver and Trendelenburg's position are common methods for producing venous distention, aiding ultrasonographically guided identification and cannulation of the jugular and common femoral veins. We hypothesize that humming is as effective as either Valsalva's maneuver or Trendelenburg's position for distention and ultrasonographic visualization of these procedurally important blood vessels. Herein, we investigate a new method of venous distension that may aid in the placement of central venous catheters by ultrasonographic guidance.
Healthy, normal volunteers aged 28 to 67 years were enrolled. Each subject's internal jugular, external jugular, and common femoral veins were measured in cross-section by ultrasonograph during rest (baseline), humming, Valsalva's maneuver, and Trendelenburg's position. Three measurements were recorded per observation in each position. Subjects were used as their own controls, and measurements were normalized to percentage increase in diameter during each maneuver or position for later comparison.
The study population consisted of 7 subjects, with a mean age of 47 years. Cross-sectional area was calculated for each vessel in 3 groups: baseline/control, Valsalva, Trendelenburg, and humming. The mean percentage change (+/-SD) relative to baseline cross-sectional area of the jugular vessels for each subject were external jugular vein: humming 134%+/-25% (95% confidence interval [CI] 124.9% to 146.9%), Valsalva 136%+/-23% (95% CI 121.3% to 147.5%), Trendelenburg 137%+/-32% (95% CI 120.7% to 156.9%); internal jugular vein: humming 137%+/-27% (95% CI 119.4% to 148.2%), Valsalva 139%+/-24% (95% CI 122.4% to 148.7%), Trendelenburg 141%+/-35% (95% CI 116.5% to 156.5%); common femoral vein: humming 131%+/-15% (95% CI 120.4% to 139.1%), Valsalva 139%+/-18% (95% CI 127.9% to 150.4%), Trendelenburg 132%+/-24% (95% CI 113.3% to 142.9%).
All 3 maneuvers distended the external jugular, internal jugular, and common femoral veins compared to baseline. There was no important difference in magnitude of cross-sectional area between any of the 3 maneuvers when compared with one another. Humming shares many physiologic similarities to Valsalva's maneuver and may be more familiar and easier to perform during procedures such as ultrasonographically guided central venous catheter placement and insertion of external jugular intravenous catheters.
Annals of emergency medicine 08/2007; 50(1):73-7. · 4.23 Impact Factor
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ABSTRACT: The accurate diagnosis of influenza remains a diagnostic dilemma. We examine the performance of various strategies for diagnosing influenza infection in an unselected sample of adults during influenza season.
Consecutive adults presenting to a university emergency department or urgent care clinic between January and March 2002 with acute respiratory complaints were eligible for this prospective observational study. The performance of clinician judgment, a rapid influenza test, and a clinical prediction rule in predicting influenza infection was evaluated using referent standard of reverse transcriptase polymerase chain reaction. Statistical significance was assessed using McNemar's test of proportions.
Fifty-three of 258 (21%) patients had a positive influenza reverse transcriptase polymerase chain reaction test. Overall, clinician judgment showed sensitivity of 29% (95% confidence interval [CI] 18% to 43%) and specificity of 92% (95% CI 87% to 95%). The rapid influenza test showed a sensitivity of 33% (95% CI 22% to 47%) and specificity of 98% (95% CI 96% to 99%). The clinical prediction rule showed a sensitivity of 40% (95% CI 27% to 54%) and specificity of 92% (95% CI 87% to 95%). Clinician judgment when patients presented within 48 hours showed a sensitivity of 67% (95% CI 39% to 86%) and specificity of 96% (95% CI 81% to 99%). Neither the rapid influenza test (P=.10) nor the clinical prediction rule (P=.42) was superior to clinician judgment alone in the diagnosis of influenza.
The suggestion that a clinical decision rule or a rapid influenza test is better than clinical judgment alone for the diagnosis of influenza in an unselected patient population is not supported by this study.
Annals of emergency medicine 12/2005; 46(5):412-9. · 4.23 Impact Factor
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ABSTRACT: To evaluate the performance of a rapid, bedside whole blood C-reactive protein test as a diagnostic test for pneumonia in adults.
We enrolled consecutive adults who presented with acute cough (duration < or =3 weeks). A fingerstick blood specimen for C-reactive protein level was obtained. Patients also provided information about demographic characteristics and symptoms. Physical examination findings, diagnoses, and treatments were abstracted from the medical record; illness duration and subsequent office visits were determined with follow-up telephone calls. A clinical prediction rule for pneumonia was calculated for each patient and compared with C-reactive protein levels.
Twenty (12%) of the 168 patients in the study had radiographic evidence of pneumonia. Median C-reactive protein levels were significantly higher for patients with pneumonia than in the remaining patients (60 mg/L vs. 9 mg/L, P <0.0001). The area under the receiver operating characteristic (ROC) curve for C-reactive protein level as a predictor of pneumonia was 0.83. C-reactive protein level and the clinical prediction rule were independently associated with pneumonia, yielding a combined area under the ROC curve of 0.93. C-reactive protein level was not associated with hospitalization or resolution of symptoms.
C-reactive protein levels could be a valuable addition to clinical prediction rules for pneumonia. A C-reactive protein level > or =100 mg/L might be a useful indication for chest radiography or empiric antibiotic therapy when the diagnosis of pneumonia is in doubt.
The American Journal of Medicine 04/2004; 116(8):529-35. · 5.43 Impact Factor
