CLN Article

Diagnostic Profiles

Most Common Use of cTnI in Children of Little Diagnostic Value

An analysis of the use of cardiac troponin I (cTnI) assays in a pediatric population found that although the test was ordered most frequently to evaluate children who presented to the emergency department (ED) with chest pain, cTnI levels were within the normal range nearly 99% of the time if the patients were afebrile and/or had normal electrocardiogram (ECG) results (Am J Cardiol 2012;110:284–89). The findings suggest that in pediatric patients presenting to the ED with chest pain but without fever or abnormal ECG results, cTnI assays are of little diagnostic or prognostic value, and represent increased resource utilization.

The authors conducted the study to assess current clinical practice, contribution to patient diagnosis and management, prognosis, and resource utilization associated with using cTnI screening in a pediatric population. The retrospective review, which covered a 7-year study period in a 23-hospital system, involved all pediatric patients ≤18 years who had cTnI levels measured. In all, 3,497 patients met the study criteria.

Compared to patients with normal cTnI levels, those with elevated values—defined as ≥0.4 ng/mL—were younger and more likely to be male. The two most common diagnoses for patients presenting with chest pain and elevated cTnI were myopericarditis (53%) and overdose or poisoning (7%). cTnI results had the highest predictive value in patients who presented with trauma or overdose or poisoning. The relative risks of ventilation and death associated with elevated levels were 2.8 and 8 in the case of trauma, and 5 and 92 in the case of overdose or poisoning.

Attenuated Link between Diabetes, FABP4 and Non-esterified Fatty Acids

New research links plasma fatty acid-binding protein 4 (FABP4) to incident type 2 diabetes, an association found to be statistically significant only in lean men (Diabetes Care 2012;35:1701–7). The authors also found a statistically significant association between non-esterified fatty acids (NEFAs) and incident type 2 diabetes in older adults during the first 5 years of follow-up but not during the mean follow-up of 9.5 years.

The research involved 3,740 subjects from the Cardiovascular Health Study, a prospective study of individuals ≥65 years in four U.S. communities who were recruited between 1989–1993 and followed every 6 months through 1999 with alternating telephone calls and clinic visits. Overall, 60% of participants were women, and the mean age at baseline was 74.8 years. The median plasma FABP4 level was 29.5 ng/mL, although women had substantially higher concentrations than men, with a median level of 34.4 ng/mL versus 22.8 ng/mL. The median NEFA concentration was 0.46 mEq/L.

The researchers found that hazard ratios increased with each standard deviation increase in log FABP4; however, after multivariate adjustment, they observed a statistically significant higher risk of diabetes mainly in men with body mass index <25 kg/m2, with a hazard ratio of 1.78. There also was a significant, positive association between NEFA and incident type 2 diabetes, but when the full follow-up period was considered, this association was attenuated and was not statistically significant, a finding that conflicts with other studies, according to the authors.

The investigators called for further studies to elucidate the mechanisms by which FABP4 may be linked to the size of adipocytes, obesity, and type 2 diabetes.

Hyperglycemia Associated with Post-Op Orthopedic Surgical Infection

Vanderbilt University researchers recently found hyperglycemia to be an independent risk factor for 30-day surgical site infection in orthopedic trauma patients without a history of diabetes (J Bone Joint Surg Am 2012;94:1181–6). The findings should focus more attention on blood glucose monitoring in orthopedic patients without a history of diabetes, about which there is presently little discussion, according to the authors.

The authors conducted the study in light of recent investigations suggesting that stress-induced hyperglycemia after trauma is strongly correlated with clinical outcomes, and research linking perioperative hyperglycemia to outcomes in general, but not orthopedic, surgical populations. Their retrospective analysis involved 790 patients selected from the institution's Trauma Registry of the American College of Surgeons database who were at least 18 years old and had isolated orthopedic injuries requiring acute operative intervention. The researchers defined hyperglycemia as either two or more random glucose values ≥200 mg/dL or a hyperglycemic index ≥1.76.

Both measures of hyperglycemia were associated with 30-day surgical site infection. Overall, 37.2% of patients had >1 glucose value ≥200 mg/dL, and of this group, 4.4% developed surgical site infection versus 1.6% whose glucose values did not meet this threshold. Similarly, 7.5% of the 134 patients with hyperglycemic index ≥1.76 developed surgical site infection versus 1.7% in patients who did not meet this criterion. A multivariable logistic regression analysis also demonstrated that two or more blood glucose levels ≥200 mg/dL was a risk factor for 30-day surgical site infection, with an odds ratio of 2.7. A second logistic regression model also found hyperglycemic index ≥1.76 to be an independent risk factor for surgical site infection, with an odds ratio of 4.9.

Procalcitonin-Guided Algorithms Cut Antibiotic Exposure in Patients with Acute Respiratory Infections

Using procalcitonin (PCT) to guide antibiotic use in patients with acute respiratory infections reduces antibiotic exposure without increasing risk of mortality or treatment failure (Clin Infect Dis 2012;55:651–62). The findings suggest that using PCT in clinical algorithms has the potential to improve antibiotic management in this patient population, and could reduce risk associated with antibiotic resistance.

The study involved a meta-analysis of clinical trials in which patients with acute respiratory infections were assigned to receive either antibiotics based on PCT algorithms or usual care. In all, the researchers identified 14 such trials involving 4,221 patients. Although PCT has shown to be useful in supporting clinical decision making around antibiotic therapy in patients with acute respiratory infections, individual trials considering this issue have lacked statistical power to assess risk of mortality and severe infectious disease complications associated with PCT-guided therapy.

Overall, 5.7% of patients assigned to PCT groups died compared with 6.3% of control patients. Treatment failure occurred in 19.1% of PCT-assigned patients versus 21.9% of controls. PCT was not associated with increased mortality or treatment failure in any clinical setting or acute respiratory illness diagnosis. However, the researchers found total antibiotic exposure per patient to be significantly reduced in PCT-guided therapy patients versus controls, with a median of 4 days compared to 8 days.

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