Robert J. Zalenski

Assessing the diagnostic value of an ECG containing leads V4R, V8, and V9: The 15-Lead ECG

STUDY OBJECTIVES To assess sensitivity, specificity, and odds ratios of ECG findings on leads V4R, V8, and V9 for acute myocardial infarction. DESIGN Prospective, two-stage cohort study. SETTING A 660-bed university-affiliated community hospital. TYPE OF PARTICIPANTS One hundred forty-nine admitted patients with suspected myocardial infarction or unstable angina. INTERVENTIONS Standard 12-lead ECG followed immediately by V4R, V8, and V9. MEASUREMENTS Initial ECG findings of ST-segment displacement, Q waves, T-wave inversion, and eligibility for thrombolytic therapy. RESULTS Major abnormalities (ST-segment deviation, T-wave inversion, Q waves) were found on the extra three leads in 28.9% (43 of 149) of patients. Sensitivity of ST-segment elevation for acute myocardial infarction on 12 versus 15 leads increased from 47.1% to 58.8%, respectively, with no decrease in specificity. McNemars pair-matched analysis for ST-segment elevation on myocardial infarction subgroup showed an association of ST elevation with the 15-lead ECG (P < .05). An eightfold increase in the odds of detecting ST elevation was found (90% confidence interval, 1.42 to 14.58); 22% of patients negative for ST elevation on 12 leads were positive on 15 leads. Analysis of ECG criteria for thrombolytic therapy presenting uniquely on extra leads showed an increased sensitivity from 35.3% to 44.1% on 12 versus 15 leads, respectively; there was a sixfold increase in the odds of meeting ECG thrombolytic therapy criteria (90% confidence interval, 0.34 to 11.66); 13.5% of patients not meeting criteria on 12 leads did so on 15 leads. CONCLUSION The 15-lead ECG provides increased sensitivity and odds of detecting ST-segment elevation in acute myocardial infarction patients with no loss of specificity; its use may expand the selection of thrombolytic therapy candidates and provide a fuller ECG description of the extent of myocardial injury and necrosis.

Risk of human immunodeficiency virus infection among emergency department workers

PURPOSE To estimate (1) the prevalence of human immunodeficiency virus (HIV) infection in emergency department (ED) patients, (2) the frequency of blood contact (BC) in ED workers (EDWs), (3) the efficacy of gloves in preventing BC, and (4) the risk of HIV infection in EDWs due to BC. PATIENTS AND METHODS We conducted an 8-month study in three pairs of inner-city and suburban hospital EDs in high AIDS incidence areas in the United States. At each hospital, blood specimens from approximately 3,400 ED patients were tested for HIV antibody. Observers monitored BC and glove use by EDWs. RESULTS HIV seroprevalence was 4.1 to 8.9 per 100 patient visits in the 3 inner-city EDs, 6.1 in 1 suburban ED, and 0.2 and 0.7 in the other 2 suburban EDs. The HIV infection status of 69% of the infected patients was unknown to ED staff. Seroprevalence rates were highest among patients aged 15 to 44 years, males, blacks and Hispanics, and patients with pneumonia. BC was observed in 379 (3.9%) of 9,793 procedures; 362 (95%) of the BCs were on skin, 11 (3%) were on mucous membranes, and 6 (2%) were percutaneous. Overall procedure-adjusted skin BC rates were 11.2 BCs per 100 procedures for ungloved workers and 1.3 for gloved EDWs (relative risk = 8.8; 95% confidence interval = 7.3 to 10.3). In the high HIV seroprevalence EDs studied, 1 in every 40 full-time ED physicians or nurses can expect an HIV-positive percutaneous BC annually; in the low HIV seroprevalence EDs studied, 1 in every 575. The annual occupational risk of HIV infection for an individual ED physician or nurse from performing procedures observed in this study is estimated as 0.008% to 0.026% (1 in 13,100 to 1 in 3,800) in a high HIV seroprevalence area and 0.0005% to 0.002% (1 in 187,000 to 1 in 55,000) in a low HIV seroprevalence area. CONCLUSIONS In both inner-city and suburban EDs, patient HIV seroprevalence varies with patient demographics and clinical presentation; the infection status of most HIV-positive patients is unknown to ED staff. The risk to an EDW of occupationally acquiring HIV infection varies by ED location and the nature and frequency of BC; this risk can be reduced by adherence to universal precautions.

Safety Evaluation and Confidence Intervals When the Number of Observed Events Is Small or Zero

A common objective in many clinical studies is to determine the safety of a diagnostic test or therapeutic intervention. In these evaluations, serious adverse effects are either rare or not encountered. In this setting, the estimation of the confidence interval (CI) for the unknown proportion of adverse events has special importance. When no adverse events are encountered, commonly used approximate methods for calculating CIs cannot be applied, and such information is not commonly reported. Furthermore, when only a few adverse events are encountered, the approximate methods for calculation of CIs can be applied, but are neither appropriate nor accurate. In both situations, CIs should be computed with the use of the exact binomial distribution. We discuss the need for such estimation and provide correct methods and rules of thumb for quick computations of accurate approximations of the 95% and 99.9% CIs when the observed number of adverse events is zero.

Human immunodeficiency virus and hepatitis B virus seroprevalence in an urban trauma population

OBJECTIVE To determine the seroprevalence of the human immunodeficiency virus (HIV) and the hepatitis B virus (HBV) in patients of an urban level I trauma center. DESIGN Prospective, blinded point prevalence study of serum HIV and HBV antibody and antigen. SETTING An urban level I trauma center that participates in a trauma system serving three million people. PATIENTS The study included 994 (94.8%) of 1049 consecutive trauma service patients treated between June 6, 1988 and September 22, 1988. The patients were 82.2% male and 73.1% black, with a mean age of 28.8 +/- 12.3 years. Blunt trauma was seen in 65.4% of patients, 5.2% were in shock, and 96.2% survived their trauma. MAIN OUTCOME MEASURES HIV and HBV seroprevalence, using both antibody and antigen testing. RESULTS HIV infection was seen in 43 patients (4.3%); 41 (95.3%) were HIV Ab+ and two (4.7%) were HIV Ab-/HIV Ag+. Infection with the HBsAg was seen in 31 patients (3.1%). Infection with either virus was seen in 70 patients (7%); four patients (0.4%) were infectious for both viruses. Infection was related to age 20 to 49 years, i.v. drug use, a hepatitis or sexually transmitted disease history, prior HIV testing, shock, and death (p < 0.05). Penetrating trauma was not predictive of infection. In a logistic regression model, IV drug use was the single significant predictor of infection (p < 0.05). CONCLUSIONS Young urban trauma patients, because of drug-related intentional violence, are 15.3 to 17.6 times more likely to be HIV infected and 3.9 to 7.9 times more likely to be infectious for HIV or HBV than the trauma population overall. The 12 to 21% infection rates in critically injured patients who require shock resuscitation and/or die reinforces the need for mandated universal precautions and for clear policies which govern the performance of procedures by physicians in training. Primary HIV infection in critically injured patients may worsen their outcome and may adversely affect the exposed health care worker. Emergency departments and trauma units should develop a referral system to HIV primary care services (HIV counselling and testing) for high risk patients and for adversely exposed health care workers.