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CAP Home > CAP TODAY > CAP TODAY 2012 Archive > Clinical Abstracts
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  Clinical Abstracts

 

 

 

 

January 2012

Editor:
Deborah Sesok-Pizzini, MD, MBA

A note to readers

For CAP TODAY “Selected Abstracts,” the new year brings with it a grateful goodbye and a warm welcome.
Contributing editor Michael Bissell, MD, PhD, MPH, has retired as the writer of the “Clinical Pathology Abstracts” column after nearly 12 years in that role. We thank him for his dedication and popular contributions to CAP TODAY. We will continue to publish in the next few months the last of the abstracts Dr. Bissell wrote.
CAP TODAY welcomes as its new “Clinical Pathology Abstracts” editor Deborah Sesok-Pizzini, MD, MBA. Dr. Sesok-Pizzini is associate professor in the Department of Clinical Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, and medical director, Blood Bank and Transfusion Medicine, Children’s Hospital of Philadelphia. In this month’s issue are the first of Dr. Sesok-Pizzini’s abstracts.

Association of Alzheimer disease pathology with abnormal lipid metabolism Association of Alzheimer disease pathology with abnormal lipid metabolism

The association between lipid profiles and developing Alzheimer disease is not established, although recent evidence suggests that the disease may be associated with metabolic disorders, such as insulin resistance and diabetes. To test the hypothesis that Alzheimer disease (AD) is also associated with dyslipidemia, the authors examined a series of autopsy samples from residents of Hisayama, Japan, during a four-and-a-half-year period to correlate neuritic plaques and neurofibrillary tangles with fasting blood sample results performed in 1988. The tests used in the study were total cholesterol (TC), low-density lipoprotein cholesterol (LDLC), high-density lipoprotein cholesterol (HDLC), and triglycerides (TG). The study included 147 patients from the authors’ registry that had fasting blood samples and brain autopsy. At the time of their initial clinical examination in 1988, the subjects did not show signs of early dementia. In an age- and gender-adjusted analysis, the subjects with neuritic plaques showed significantly higher TC, LDLC, TC/HDLC, LDLC/HDLC, and non-HDLC levels. Further analysis showed that adjusting for APOE genotype resulted in an increased risk of neuritic plaques and that subjects with the highest lipid values (quartiles) had an increased risk for neuritic plaques compared with those in the lowest quartiles. These results were not observed in the subjects without such plaques. In contrast, no association was found between any lipid profile and neurofibrillary tangles. The authors suggested that lipid profiles may result in a threshold effect in which Alzheimer disease neuritic plaque formation is more likely. Therefore, controlling lipid levels below a certain value could decrease the risk of such plaques and may help prevent Alzheimer disease. The possible threshold values as a result of this study are 6 mmol/L for TC and 4 mmol/L for LDLC. The authors did note that the study was limited by the fact that the lipid profiles were determined in peripheral blood and that this may not be the same as cholesterol metabolism in the brain. Furthermore, the small sample size may have resulted in the lack of association between lipid profiles and neurofibrillary tangles. The authors concluded that additional studies are needed to prove the causal link between dyslipidemia and developing neuritic plaques and Alzheimer disease-related signs and symptoms.

Matsuzaki T, Sasaki K, Hata J, et al. Association of Alzheimer disease pathology with abnormal lipid metabolism. Neurology. 2011; 77:1068–1075.

Correspondence: Dr. Kensuke Sasaki at ksasaki@np.med.kyushu-u.ac.jp

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Use of molecular assays in diagnosis of neonatal sepsis Use of molecular assays in diagnosis of neonatal sepsis

Recent trends toward molecular testing as a replacement for viral and bacterial culture have changed the platform of testing for many laboratories. With these advancements, labs can perform tests more efficiently and rapidly, generating test results in less than 12 hours. This can be critical in the more elusive diagnosis of conditions such as neonatal sepsis. Neonatal sepsis affects very low birth weight infants within the first 72 hours of life and may be life threatening in as many as 36 percent of infants with gram-negative sepsis. Early detection and treatment of neonatal sepsis is critical to generating favorable outcomes and avoiding associated morbidities, such as patent ductus arteriosus, bronchopulmonary dysplasia, and necrotizing enterocolitis. Microbial cultures of blood or other sterile fluids are the gold standard in the diagnosis of neonatal sepsis. The limitations of using culture include low amounts of bacteremia in neonates, antibiotics given intrapartum, and long turnaround times for specific species identification. The authors performed a systematic review to determine if molecular testing had sufficient sensitivity (greater than 0.98) and specificity (greater than 0.95) to replace traditional microbial cultures for the diagnosis of neonatal sepsis. They analyzed subgroups by type of assay, gestational age of the neonate, and type of sepsis onset. Two reviewers assessed the methodological quality of the studies that evaluated molecular assays in neonates with suspected sepsis in comparison with microbial cultures. Results were interesting with regard to findings of sensitivity and specificity with the molecular assays. Of the 23 studies included, the mean sensitivity and specificity were 0.90 (95 percent confidence interval, 0.78–0.95) and 0.96 (95 percent confidence interval, 0.94–0.97), respectively. Real-time polymerase chain reaction and broad-range conventional PCR had the highest sensitivity and specificity. Sufficient data were not available to evaluate gestational-age and sepsis-type subgroups. Based on these results, the authors concluded that molecular assays should not replace culture in the diagnosis of neonatal sepsis. However, adding molecular assays in conjunction with conventional culture methods may help identify neonatal sepsis in the early stages, although molecular assays alone are unable to provide information about antibiotic susceptibility.

Pammi M, Flores A, Leeflang M, et al. Molecular assays in the diagnosis of neonatal sepsis: a systematic review and meta-analysis. Pediatrics. 2011;128(4):e973–e985.

Correspondence: Dr. Mohan Pammi at mohanv@bcm.edu

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Detecting H1N1 virus using reverse transcription polymerase chain reaction Detecting H1N1 virus using reverse transcription polymerase chain reaction

Soon after emergence of the 2009 pandemic influenza A (H1N1) virus, the World Health Organization provided diagnostic kits and the information necessary to develop polymerase chain reaction (PCR) assays to identify this novel virus. The authors evaluated real-time PCR formats for their ability to detect the 2009 pandemic H1N1 virus in clinical specimens. Hemagglutinin and nonstructural genes were chosen as targets for these assays. The nucleotide sequences of these genes are sufficiently distinct from those of recently circulating seasonal H1N1 and other influenza viruses and offer opportunities to design primers and probes that specifically amplify hemagglutinin and nonstructural gene segments of the pandemic virus. Nonstructural gene-specific assays could be particularly useful should the virus mutate to a degree where current hemagglutinin-based PCR assays lose sensitivity. Combined nasal and throat swabs from 343 patients infected with the 2009 H1N1 virus and 32 quality assessment samples were available. An H1N1 virus (A/Finland/554/2009) isolate was propagated in MDCK cells, and the culture supernatant was stored in aliquots at –70°C and used as a positive control. PCR assays targeting different regions of the nonstructural (SW-NS-60, SW-NS-183, SW-NS-631) and hemagglutinin (SW-H1-674, SW-H1-1076) genes of the H1N1 virus were developed. A matrix gene-specific PCR assay, designated the IA M1 assay, which detects all subtypes of influenza A virus, served as the reference method. The CDC SW H1 HA-specific PCR assay was included in some experiments. The authors found that real-time reverse transcription PCR assays specific for the nonstructural and hemagglutinin genes of the 2009 H1N1 virus were characterized by high specificity and sensitivity. The tests performed well during the first year of the 2009 pandemic.

Ronkko E, Ikonen N, Kontio M, et al. Validation and diagnostic application of NS and HA gene-specific real-time reverse transcription-PCR assays for detection of 2009 pandemic influenza A (H1N1) viruses in clinical specimens. J Clin Microbiol. 2011;49:2009–2011.

Correspondence: Esa Ronkko at esa.ronkko@thl.fi

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Thyroglobulin levels in thyroid cancer patients Thyroglobulin levels in thyroid cancer patients

The treatment of differentiated thyroid carcinoma for most patients consists of total or near-total thyroidectomy followed by 131I remnant ablation and thyroid hormone suppression. After 131I remnant ablation, the measurement of serum thyroglobulin (Tg) levels forms the basis of postablation followup, together with cervical ultrasound. Measurement of serum Tg levels at the time of 131I remnant ablation—that is, four to six weeks after thyroidectomy—proved to be useful for predicting the early and long-term outcome of patients. However, recurrences and metastases on the 131I post-treatment whole-body scan (PT-WBS) were reported in 6.3 percent to 8.5 percent of patients with an undetectable preablative Tg value. The fundamental role of Tg measurement in the postoperative monitoring of differentiated thyroid carcinoma (DTC) implies the need for high-quality Tg assays. A major problem that hampers accurate Tg measurement is interference in the Tg assay by Tg antibodies (TgAb) and heterophile antibodies (HAb), resulting in an under- or overestimation of the serum Tg concentration. Immunometric Tg assays may also be subject to high-dose hook effect, leading to inappropriately normal or low serum Tg values in sera with very high Tg concentrations, which require dilution for accurate measurement. Furthermore, undetectable serum Tg becomes detectable in a significant percentage of DTC patients by switching assays, suggesting that, in many patients, a decrease in immunologic reactivity or structural changes of the Tg molecule cause the undetectable Tg levels. The precise incidences of these sources of failure in Tg measurement have never been documented comprehensively in the preablative setting. Therefore, the authors conducted a study to evaluate the role of assay interferences and Tg immunoreactivity in causing inappropriately undetectable Tg values among DTC patients with a positive PT-WBS. The authors selected 47 patients with undetectable serum Tg but residual 131I uptake on a PT-WBS from 298 consecutive patients with histologically proven DTC. Interferences from anti-thyroglobulin antibodies (TgAb), heterophile antibodies, and hook effects were screened. In the remaining samples, serum Tg was measured in three different immunoassays. The authors found that of 47 patients, 11 (23 percent) showed interference from thyroglobulin antibodies (n=10) or heterophile antibodies (n=1). Among the 36 remaining patients, 18 showed detectable Tg levels after retesting using a different immunoassay, whereas the remaining 18 patients also showed detectable Tg levels in a third Tg immunoassay. However, only seven patients showed a detectable Tg in both assays used secondarily. Tg levels remained undetectable in all methods in nine patients (19 percent), even after extensive laboratory workup and despite the presence of 131I-avid tissue found in PT-WBS. The authors concluded that a careful assessment of interferences in Tg measurement significantly reduced the occurrence of undetectable Tg among patients with 131I uptake in PT-WBS. However, such extensive assessment is difficult in clinical practice, and one-fifth of patients still had undetectable Tg in multiple assays despite the intensive laboratory workup. A benchmark between 131I imaging and Tg measurement authenticates the interpretation of Tg measurements and, therefore, continues to be of pivotal value by authenticating the use of serum Tg during further followup of DTC patients.

Giovanella L, Suriano S, Ceriana L, et al. Undetectable thyroglobulin in patients with differentiated thyroid carcinoma and residual radioiodine uptake on a postablation whole-body scan. Clin Nuc Med. 2011;36:109–112.

Correspondence: Dr. Luca Giovanella at luca.giovanella@eoc.ch

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Emergency department lab turnaround time Emergency department lab turnaround time

The length of stay in the emergency department is a surrogate index of overcrowding, despite many factors that can influence it. Laboratory turnaround time and time from drawing blood samples to reporting patient results to physicians are regarded as some of the most important determinants of length of stay. During the last decade, advances in bioengineering have shortened the turnaround time of the complete blood cell count to less than 30 minutes. On the other hand, blood chemistry, one of the most frequent emergency laboratory tests, still takes more than 30 minutes in more than 90 percent of cases. In previous studies, point-of-care testing (POCT) and use of satellite laboratories near emergency departments were shown to reduce turnaround time. However, most of these studies focused only on certain diseases and associated laboratory results, such as urine human chorionic gonadotropin for pregnancy and serum troponin for acute myocardial infarction. Therefore, it’s hard to generalize these results to other emergency department patients. A routine emergency blood chemistry includes a liver panel, renal panel, pancreatic enzyme, and electrolytes. Blood gases and a lipid panel may be added for some patients. The turnaround time of blood chemistry is often regarded as the rate-determinant process. Therefore, POCT using a comprehensive chemistry analyzer may improve clinical decision time, thereby improving the throughput process in the emergency department. The authors conducted a study in which they compared the effect of POCT and central laboratory testing on the speed of specimen turnaround and clinical decisions for patients who needed blood chemistry testing. This was a randomized controlled multicenter trial in the emergency departments of five academic teaching hospitals. The authors randomly assigned patients to POCT or central lab testing stratified by the Emergency Severity Index. A POCT chemistry analyzer (Piccolo from Abaxis), which is able to test liver panel, renal panel, pancreas enzymes, lipid panel, electrolytes, and blood gases, was set up in each emergency department. Primary and secondary endpoints were turnaround time and door-to-clinical-decision time. A total of 2,323 patients were randomly assigned to either the POCT group (n=1,167) or central lab testing group (n=1,156). All basic characteristics were similar in the two groups. The turnaround time (median, interquartile range [IQR]) of the POCT group was shorter than that of the central lab testing group (14, 12 to 19 versus 55, 45 to 69 minutes; P<0.0001). The median (IQR) door-to-clinical-decision time was also shorter in the POCT group compared with the central lab testing group (46, 33 to 61 versus 86, 68 to 107 minutes; P<0.0001). The proportion of patients who had new decisions within 60 minutes was 72.8 percent for the POCT group and 12.5 percent for the central lab testing group (P<0.0001). The authors concluded that a POCT chemistry analyzer in the emergency department shortens test turnaround times and emergency department clinical decision times compared with central lab testing.

Lee EJ, Shin SD, Song KJ, et al. A point-of-care chemistry test for reduction of turnaround and clinical decision time. Am J Emerg Med. 2011;29:489–495.

Correspondence: Dr. Sang Do Shin at shin sangdo@medimail.co.kr

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Laboratory findings for recurrent abdominal pain Laboratory findings for recurrent abdominal pain

A pivotal paper on recurrent abdominal pain, written by John Apley and Nora Naish and published in 1958, defined such pain as at least three bouts of abdominal pain during a period of at least three months that was severe enough to interfere with daily activities. Apley and Naish found that 10.8 percent of students in a school population had recurrent abdominal pain (RAP) but found no suspicion of organic disease to explain the pain. A considerable number of children and their families, however, showed psychological problems. The authors of the paper suggested that emotional disturbances might play an important role in the pathogenesis of abdominal pain. This form of abdominal pain was considered to be functional. In the last decade, experts in the field of pediatric gastroenterology attempted to set criteria for functional gastrointestinal disorders in childhood, including abdominal pain, called the Rome criteria. These criteria are based on a complex of symptoms and, importantly, exclusion of organic causes of the pain. However, there are no guidelines regarding which organic causes have to be excluded before a functional disorder can be diagnosed according to the Rome criteria. Reported attempts to identify somatic causes of RAP are relatively scarce. In the past, somatic causes of RAP were found by Apley in two series, in six percent to eight percent of subjects. More recently, using new techniques, organic abnormalities were found in 25 percent to 45 percent of children with RAP. The prevalence of RAP in children varies from less than one percent to 39 percent in population-based studies. This difference could be related to the varying definitions of RAP and differences in the methodologies to assess the diagnosis. The authors performed a prospective study of children presenting with RAP who were referred by their general physicians to a secondary care clinic to evaluate characteristics of pain, concomitant symptoms, and results of diagnostic tests. The intent of the study was to assess the percentage of possible organic causes of RAP in children with abdominal pain who were worked up with a similar protocol. The authors evaluated consecutive patients with RAP (Apley criteria) who were aged four to 16 years and referred to a secondary medical center. They assessed the patients using a standardized history, physical examination, and laboratory tests. The tests encompassed Helicobacter pylori, gastrointestinal bacterial infections, protozoa, celiac disease, carbohydrate malabsorption, and food intolerance and involved abdominal ultrasound and abdominal x-ray. More investigations were obtained if indicated. Patient characteristics were compared against those of surgical patients without abdominal pain (control group). The study involved 220 consecutive patients (92 males and 128 females; mean age, 8.8 years [range, 4.1 to 16 years]). In 88 percent of the patients, abnormalities were found that referred to possible causes. Protozoa were present in 33 percent of the patients and were primarily Dientamoeba fragilis. Yersinia enterocolitica was found in 12 percent and endoscopically proven infection with Helicobacter pylori in 11 percent. In 36 percent, an abdominal x-ray raised suspicion of constipation. The authors concluded that in 220 consecutive patients with RAP who were referred to secondary care, a standardized workup yielded abnormal results in a high percentage. The clinical significance of these findings remains to be established.

Gijsbers CFM, Benninga MA, Buller HA. Clinical and laboratory findings in 220 children with recurrent abdominal pain. Acta Paediatr. 2011;100:1028–1032.

Correspondence: Dr. Carolien F. M. Gijsbers at c.gijsbers@hagaziekenhuis.nl or cfm.gijsbers@planet.nl

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How detecting AmpC beta lactamase affects patients How detecting AmpC beta lactamase affects patients

Escherichia coliandKlebsiella pneumoniae containing plasmid-mediated AmpC b-lactamases have been associated with treatment failure in a case-control study of bacteremia when compared with organisms without plasmid-mediated AmpC b-lactamases. A treatment failure rate of almost 52 percent for AmpC-containing K. pneumoniaebloodstream isolates at 72 hours has been reported. Unfortunately, plasmid-mediated AmpC b-lactamases are not reliably detected by standard susceptibility testing methods in the clinical microbiology laboratory. The EDTA disk test and the modified Hodge test for detecting AmpC b-lactamases could be carried out routinely in a busy clinical laboratory. A similar test using boronic acid has been described. However, none of these tests can distinguish plasmid-mediated hyperproduction of AmpC from derepressed chromosomal or any other mechanism of overproduction of an AmpC b-lactamase. The authors believe the mechanism of AmpC overproduction should not matter for clinical outcome because, either way, such organisms should be resistant to all extended-spectrum cephalosporins, although perhaps not to the advanced-spectrum cephalosporins of cefepime and cefpirome. The authors compared the clinical outcomes for 26 (23 evaluable) patients with bacteremic gram-negative isolates with overproduction of AmpC, as measured by the modified Hodge test, against 52 (51 evaluable) control patients whose isolates did not produce AmpC. They tested 753 gram-negative bloodstream isolates for AmpC using the EDTA disk test and the modified Hodge test (n=172) and the modified Hodge test alone (n=581). The 30-day mortality for the AmpC group was nine percent; it was six percent for the control group. Clinical response was similar: afebrile on day two (AmpC group, 70 percent; control group, 71 percent) and day four (AmpC group, 86 percent; control group, 84 percent). Patients with isolates in the AmpC group were more likely to be in an intensive care unit at the time of positive blood culture (P=0.01) and more likely to be intubated (P=0.05) than patients with isolates in the control group. Effective antibiotic treatment within the first 48 hours was given to 47 of 51 (92 percent) patients with isolates in the control group but to only 14 of 23 (61 percent) patients with isolates in the AmpC group (P=0.001). The authors concluded that the modified Hodge test and the EDTA disk test did not identify patients at risk for a poor outcome from AmpC-producing bacterial infections.

Rand KH, Turner B, Seifert H, et al. Clinical laboratory detection of AmpC b-lactamase: Does it affect patient outcome? Am J Clin Pathol. 2011;135:572–576.

Correspondence: Dr. Kenneth H. Rand, University of Florida College of Medicine, Dept. of Pathology, Immunology and Lab Medicine, P. O. Box 100275, Gainesville, FL 32601-0275

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Screening newborns for hemoglobin H disease Screening newborns for hemoglobin H disease

The United States Secretary of Health and Human Services Advisory Committee on Heritable Disorders in Newborns and Children (SACHDNC) recommends which conditions the individual states should include in their newborn screening panels. The recommendations are based on findings from systematic evidence reviews of the expected net benefit of directly screening neonates. The only hemoglobinopathy recommended for screening is sickle cell disease. However, other potentially clinically significant hemoglobin variants can be detected when screening for sickle cell disease, such as hemoglobin (Hb) H disease. Hb H disease results from deletions or nondeletional mutations, or both, affecting three of the four α-globin genes, leading to an excess of β-globin production and the formation of β-tetramers, known as Hb H. Hb H disease is associated with a range of adverse health effects, including growth retardation, splenomegaly, cholelithiasis, and iron overload. Nondeletional Hb H disease, especially with the constant spring mutation, usually has an earlier clinical presentation and more severe disease course. Several states, including California, Hawaii, Missouri, and Washington, screen newborn infants for Hb H disease. Population screening is based on detecting y-tetramers, known as Hb Bart’s, which are only present in significant quantity in the first month of life in newborn infants with α-thalassemia. Newborn screening is especially appealing because Hb H disease is identified by the abundance of Hb Bart’s and is only possible in the newborn period, before y-globin production switches to β-globin. To assist the SACHDNC in determining whether Hb H disease screening should be recommended as part of the states’ core testing panel, the authors conducted a systematic evidence review regarding the potential benefits and harms of newborn screening. They identified 21 articles in Medline from 1989 to March 2010 that provided evidence regarding screening, treatment, and outcomes associated with Hb H disease. The authors found that in California, newborn screening had identified nine cases per 100,000 of deletional Hb H disease and 0.6 cases per 100,000 of nondeletional Hb H disease. Five cases of hemoglobin Bart’s hydrops fetalis syndrome were also identified in over 10 years of screening for Hb H disease. Although Hb H disease is associated with a wide range of morbidity, no studies were found that evaluated the benefits of early identification and treatment. The SACHDNC found the data insufficient to recommend that states adopt newborn screening for Hb H disease.

Kemper AR, Knapp AA, Metterville DR, et al. Weighing the evidence for newborn screening for hemoglobin H disease. J Pediatr. 2011;158:780–783.

Correspondence: Dr. Alex Kemper at alex.kemper@duke.edu

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