Return to CAP Home

  Clinical Abstracts

 

 

 

 

November 2010

Editor:
Michael Bissell, MD, PhD, MPH

Use of bronchoalveolar lavage fluid galactomannan to diagnose IPA in select patients Use of bronchoalveolar lavage fluid galactomannan to diagnose IPA in select patients

Invasive filamentous fungal infections, which are mainly due to Aspergillus species, have emerged as important causes of morbidity and mortality in patients with hematologic disorders and in allogeneic stem cell transplant recipients. Many hematology and transplant centers have adopted an antifungal therapy approach based on the presence of suggestive lesions on thoracic computed tomography scans, although this strategy is limited by a lack of specificity for invasive pulmonary aspergillosis (IPA). Moreover, the classic halo and air crescent signs, which are frequently encountered among neutropenic hosts with IPA, are far less common and specific in nonneutropenic patients and transplant recipients. Ideally, these radiologic tools should be complemented by a highly specific and sensitive micro-biologic test. Aspergillus galactomannan (GM) antigen detection in serum by the Bio-Rad Platelia sandwich enzyme immunoassay (EIA) has been studied extensively and has been wide-ly accepted as a sensitive method for prospective surveillance in patients with hematologic malignancies at risk for invasive aspergillosis. Being an early indicator of disease, antigen can be detected in blood before clinical or radiologic features of disease appear. Bronchoalveolar lavage (BAL) is widely used to evaluate patients with unexplained pulmonary lesions, although the diagnostic yield of BAL fluid for detecting IPA by culture and direct examination is limited. However, a recent prospective study from the authors’ medical center evaluated the sandwich EIA to detect GM in BAL fluid from a mixed population of 24 neutropenic and 86 nonneutropenic critically ill patients at risk for invasive aspergillosis, yielding sensitivities of 90 percent and 88 percent, respectively. To further investigate the utility of GM in BAL fluid for diagnosing IPA in hematology patients, the authors conducted a retrospective analysis of the Platelia assay on BAL samples from 99 evaluable high-risk hematology patients, including 58 with proven or probable IPA. They found that BAL GM demonstrated an improved sensitivity profile (91.3 percent with an optical density index cutoff of 1.0 or greater) compared with culture and microscopy (50 and 53.3 percent, respectively). The diagnostic accuracy, as given by the area under the receiver operating characteristic curve, was 0.93 (95 percent confidence interval, 0.88–0.99). Further de-creasing the optical density index cutoff to 0.5 or greater compromised specificity more than it improved sensitivity. Estimates of the positive and negative predictive values of the Platelia assay on BAL samples (optical density index, 1.0 or greater) were 76 percent and 96 percent, respectively. The mean BAL GM optical density index did not differ in neutropenic versus nonneutropenic patients (3.9 and 4.5, respectively; P = 0.3). However, a trend toward decreased sensitivity in patients receiving mold-active pro-phylaxis was noted. The authors concluded that BAL GM is a valuable adjunctive diagnostic tool to other conventional microbiologic and radiologic studies.

Maertens J, Maertens V, Theunissen K, et al. Bronchoalveolar lavage fluid galactomannan for the diagnosis of invasive pulmonary aspergillosis in patients with hematologic diseases. Clin Infect Dis. 2009;49:1688–1693.

Correspondence: Dr. Johan Maertens at johan.maertens@uz.kuleuven.ac.be

[ Top ]

Unique finding of an H1N1 influenza virus-positive clinical sample Unique finding of an H1N1 influenza virus-positive clinical sample

The 2009 H1N1 influenza virus rapidly spread worldwide. It was predicted that, this year, the 2009 H1N1 and seasonal influenza viruses would coexist for a period of time. Rapid and accurate laboratory detection of influenza virus and its subtype is very important for selecting appropriate antiviral therapy and initiating infection control measures for hospitalized patients. However, with limited useful assays available, this is a challenging task. While quick and easy to perform, rapid influenza virus antigen-detection assays are known to suffer from low sensitivity for the 2009 H1N1 virus. Reverse transcription-polymerase chain reaction (RT-PCR) is not only sensitive compared to virus culture but also much more rapid than culture and, therefore, widely used. The authors reported on a highly unusual case of 2009 H1N1 influenza involving a four-year-old girl who presented with a week-long history of persistent wheezing. On Oct. 25, 2009, the patient was admitted through the emergency room because of one day of fever, cough, rhinorrhea, and labored breathing. She was treated with oseltamivir and supportive therapy. Her condition substantially improved, and she was discharged one day after admission. While her history was unremarkable, her laboratory results from viral assays were very interesting. The nasopharyngeal as-pirate/wash fluid as well as the naso-pharyn-geal swab collected at admission tested positive for influenza A virus by the Binax rapid antigendetection assay (Inverness Medical). However, RT-PCR analysis of the same nasopharyngeal specimen with the ProFlu+ assay (Gen-Probe Prodesse) was negative for influenza A and B viruses and respiratory syncytial virus. To investigate these findings further, influenza A virus subtyping by PCR and virus culture were conducted. Surprisingly, the same nucleic acid extract that had been negative for influenza virus by the ProFlu+ assay was strongly positive for 2009 H1N1 influenza virus by the ProFlu-ST assay, with a cycle threshold of 17. A shell vial culture with R-Mix cells (Diagnostic Hybrids) and a tube culture with rhesus monkey kidney cells stained positive for influenza A virus with a Bartels viral respiratory screening and identification kit (Trinity Biotech). Upon repeated RT-PCR assays of the nasopharyngeal cell culture supernatant, results were the same as those obtained by testing the initial nasopharyngeal specimen—that is, the ProFlu+ assay was negative for influenza A and B viruses but the ProFlu-ST assay was positive for 2009 H1N1 influenza virus. Split samples from the same cell culture supernatant were also run independently in two other institutions and the results remained the same. The same cell culture supernatant was referred to the Illinois Department of Public Health laboratories for testing using the CDC RT-PCR assay. This sample was positive for novel influenza A virus (H1N1) RNA. (All three reactions with InfA, swInfA, and swH1 primer-probe sets were positive.) The same sample tested positive for influenza A virus using MultiCode-RTx influenza A/B reagents (EraGen Biosciences) and was also identified as positive for 2009 H1N1 influenza virus using a laboratory-developed assay for subtyping. The assay was performed at Evanston Hospital, Evanston, Ill., a member of the NorthShore University Health Systems. The authors believe this is the first report of a sample that may indicate a mutation in the influenza A virus matrix gene. Although such a mutation seems to be very rare, the prevalence of this variant among all 2009 H1N1 viruses is unknown because of a lack of sufficient data. Because of the implication of misidentification with a single assay, this case underscores the need for cautious interpretation and additional testing when a negative RT-PCR result does not seem to fit the clinical presentation.

Zheng X, Todd KM, Yen-Lieberman B, et al. Unique finding of a 2009 H1N1 influenza virus-positive clinical sample suggests matrix gene sequence variation. J Clin Microbiol. 2010;48:665–666.

Correspondence: Xiaotian Zheng at x-zheng@northwestern.edu

[ Top ]

Vitamin D receptor polymorphisms and cancer Vitamin D receptor polymorphisms and cancer

A recent meta-analysis showed that patients with the vitamin D receptor polymorphism FokI (rs2228570) TT genotype had a significantly higher risk of developing ovarian cancer as well as prostate, breast, skin, nonHodgkin lymphoma, and colorectal cancer than those with its CC genotype. Moreover, combined results from four case-control studies showed almost the same results regarding enhanced susceptibility to ovarian cancer. However, the risk of developing ovarian cancer based on the FokI genotype is minor, and study findings are controversial. It recently has been shown that the T allele of VDR FokI polymorphisms was associated with significantly worse survival in patients with advanced nonsmall cell lung cancer. This is the first report to show a relationship between VDR polymorphisms and prognosis for patients with cancer. Although some articles identify an association between FokI polymorphisms and susceptibility to epithelial ovarian cancer (EOC), no report has identified a relationship between FokI polymorphisms and survival of patients with such cancer. Therefore, the authors investigated whether VDR FokI polymorphisms influenced the prognosis of patients with epithelial ovarian cancer. VDR polymorphisms from FokI in 101 patients with such cancer were genotyped by sequencing. Overall survival was compared between the FokI single nucleotide polymorphism using Kaplan-Meier survival curves with log-rank tests and the Cox proportional hazard model adjusted for ages, sta-ges, histology, and existence of residual tumor. The authors found that the FokI CC genotypes were associated with better prognosis compared with the CT and TT genotypes (log-rank test, P=0.008; adjusted hazard ratio, 0.18; 95 percent confidence interval, 0.05–0.61, P=0.006). The authors concluded that the VDR polymorphisms from the FokI genotype may be associated with improved prognosis for patients with epithelial ovarian cancer.

Tamez S, Norizoe C, Ochiai K, et al. Vitamin D receptor polymorphisms and prognosis of patients with epithelial ovarian cancer. Brit J Cancer. 2009;101:1957–1960.

Correspondence: M. Urashima at urashima@jikei.ac.jp

[ Top ]

Value of plasma biomarkers in pediatric heart failure Value of plasma biomarkers in pediatric heart failure

Although many biomarkers have been studied extensively in adults with structurally normal hearts, whether these correlate with heart failure in infants and young children with single-ventricle physiology is not known. The etiology of adult heart failure is typically coronary heart disease, while heart failure in these children is presumed to be due to primary myocardial dysfunction. Furthermore, in the patient with a single ventricle, ventricular “cross talk” might be compromised or even absent. These important pathophysiologic differences make it difficult to extrapolate adult data to pediatric patients with a single ventricle. The authors proposed that B-type natriuretic peptide, endothelin-1, high-sensitivity C-reactive protein, and/or cardiac troponin I plasma levels in children with single-ventricle heart disease could serve as biomarkers for heart failure. To test this hypothesis, they conducted a single-site, cross-sectional observational study of young patients with a single ventricle. Clinical heart failure was defined as a Ross score greater than two. The association of several candidate biomarkers with heart failure was assessed using logistic regression analysis and receiver operating characteristic curves. Of the 29 children included in the study, nine (31 percent) were in clinical heart failure. A doubling of plasma B-type natriuretic peptide was associated with an odds ratio for heart failure of 2.17. The area under the receiver operating characteristic curve was 80.3 percent. A threshold value of 30 pg/mL or more showed sensitivity and specificity for heart failure. Three other candidate biomarkers were not associated with clinical heart failure in this sample. The authors concluded that plasma B-type natriuretic peptide is a sensitive biomarker for clinical heart failure in young children with single-ventricle heart disease. Use of this plasma biomarker might help detect heart failure in these complex patients.

Shah A, Feraco AM, Harmon C, et al. Usefulness of various plasma biomarkers for diagnosis of heart failure in children with single ventricle physiology. Hum Pathol. 2010;41:286–292.

Correspondence: Harold Bernstein at harold.bernstein@ucsf.edu

[ Top ]


Clinical pathology abstracts editor: Michael Bissell, MD, PhD, MPH, professor, Department of Pathology, Ohio State University, Columbus.