Improved specificity of myoglobin plus carbonic anhydrase assay versus that of creatine kinase-MB for early diagnosis of acute myocardial infarction.

STUDY OBJECTIVE: Carbonic anhydrase III (CA-III) is an enzyme released from skeletal muscle in a fixed ratio with myoglobin during cell injury, but unlike myoglobin it is not found in cardiac muscle. This study compared the clinical utility of serum myoglobin (S-Mgb) in conjunction with the ratio of S-Mgb to CA-III (S-Mgb/CA-III) versus creatine kinase-MB (CK-MB) for the early diagnosis of acute myocardial infarction (AMI). METHODS: This prospective observational study set at a university teaching hospital emergency department enrolled 251 consecutive consenting patients who presented with symptoms consistent with cardiac ischemia or infarction of less than 12 hours' duration. Patients with trauma or kidney failure were excluded. Standardized history and physical examination data were recorded, as were the results of serial blood sampling for S-Mgb, CA-III, and CK-MB at 0, 1, and 3 hours after patient presentation. A positive test for the study assays was defined as an S-Mgb concentration of more than 110 ng/mL with an S-Mgb/CA-III of 3.21 or higher by receiver operating characteristic analysis. Data were analyzed with McNemar's chi 2 test for symmetry and confidence intervals (CIs), using the exact method. RESULTS: Thirty (12%) of the 251 patients were found to have AMI by World Health Organization criteria. Mean time from symptom onset to presentation was 3.2 hours. The use of S-Mgb plus S-Mgb/CA-III compared with CK-MB for identification of AMI in patients presenting within 3 hours of symptom onset yielded respective sensitivities of 47.8% versus 17.4% (P = .02); specificities of 98.9% versus 100% (P = NS); positive predictive values of 84.6% (95% CI, 54.6% to 98.1%) versus 100% (95% CI, 39.8% to 100%); and negative predictive values of 93.5% (95% CI, 90.0% to 96.6%) versus 90.0% (95% CI, 84.8% to 93.9%). CONCLUSION: S-Mgb in conjunction with S-Mgb/CA-III was significantly more sensitive than CK-MB yet equally as specific for the early diagnosis of patients with AMI.

Evaluation of a new rapid quantitative immunoassay for serum myoglobin versus CK-MB for ruling out acute myocardial infarction in the emergency department.

STUDY OBJECTIVE: To compare the predictive values of serum myoglobin and creatine kinase (CK)-MB for ruling out acute myocardial infarction in the emergency department. DESIGN: Prospective, observational study. SETTING: University teaching hospital. PARTICIPANTS: One hundred eighty nine consecutive patients aged 30 years and older who presented within 12 hours from onset of chest discomfort, dyspnea, syncope, congestive heart failure, symptomatic dysrhythmia, pulmonary edema, or epigastric pain were entered into the study. Patients with trauma or renal failure were excluded. INTERVENTIONS: Standardized history and physical examination and blood sampling for serum myoglobin (S-Mgb) and CK-MB were done at the time of presentation (T0) and 1 hour later (T1). RESULTS: Using World Health Organization criteria, 22 acute myocardial infarction patients were identified. Mean time from symptom onset to presentation was 3.2 hours. S-Mgb was more sensitive than CK-MB at T0 and T1, 55% versus 23% (P < .05) and 73% versus 41% (P < .05), respectively. Respective specificities of S-Mgb versus CK-MB were 98% versus 99% (P = NS) at T0 and 97% versus 99% (P = NS) at T1. Negative predictive values of S-Mgb versus CK-MB were 94% versus 91% (P = NS) at T0 and 96% versus 93% (P = NS) at T1. The S-Mgb assay yielded quantitative results allowing the difference between the T0 and T1 values to be analyzed. A difference of 40 or more ng/mL between T0 and T1 was considered positive. When using a positive result in either the T0 or T1 value or a difference between the two values of 40 or more ng/mL, the sensitivity of S-Mgb was 91% (P < .05 versus CK-MB), the specificity was 96% (P = NS versus CK-MB), and the negative predictive value was 99% (95% confidence interval for S-Mgb, 97.0 to 100 versus CK-MB, 95% confidence interval, 88.9 to 96.6). CONCLUSION: In the first hour of presentation to the ED, the rapid quantitative assay for S-Mgb was statistically more sensitive than CK-MB and had an excellent negative predictive value for ruling out acute myocardial infarction in patients with typical or atypical symptoms. Due to the relatively small sample size, we could not exclude the possibility that differences in specificity might become statistically significant (beta error) with a larger sample size of acute myocardial infarction patients.

Theophylline toxicity.

Theophylline toxicity continues to be a commonly encountered clinical problem. Patients may present with a vast array of toxic manifestations, including life-threatening cardiovascular and neurologic toxicity. Despite the considerable attention this topic has received in the literature, there remain some important controversies regarding the identification of high risk patients and how best to manage them. This review attempts to summarize the current state of knowledge regarding theophylline toxicity with special emphasis on toxic manifestations and the role of elimination enhancing modalities.

Massive subgaleal hematoma following minor head trauma.

A 23-month-old child developed massive head swelling secondary to a subgaleal hematoma several days following minor head trauma. When seen in the emergency department, the child was felt to be otherwise well and hemodynamically stable and was discharged with close follow-up. The hematoma subsequently resolved over the ensuing two weeks. This case represents an uncommon, but dramatic complication of minor head trauma and serves to illustrate the need for physicians to recognize this entity as well as manage it effectively. The major pitfalls in managing these patients are failure to recognize this entity and, particularly in the infant, failure to carefully assess the hemodynamic status.