Lokinendi V. Rao

Gadolinium magnetic resonance contrast agents produce analytic interference in multiple serum assays

Gadolinium magnetic resonance contrast agents are known to interfere with some clinical chemistry tests, particularly colorimetric assays for serum calcium. We studied the effects of 4 agents, gadodiamide, gadoversetamide, gadopentetate dimeglumine, and gadoteridol, for interference with multiple serum assays. Gadodiamide and gadoversetamide produced clinically significant negative interference with colorimetric assays for serum angiotensin-converting enzyme, calcium, and zinc. These agents produced clinically significant positive interference in magnesium and total iron binding capacity assays and both positive and negative interference in iron assays. Gadopentetate dimeglumine produced a negative interference with iron assays, and gadopentetate dimeglumine and gadoteridol produced negative interference with a colorimetric zinc assay. Caution should be exercised when using colorimetric assays for angiotensin-converting enzyme, calcium, iron, magnesium, total iron binding capacity, and zinc in serum samples from patients who have recently received magnetic resonance contrast agents. In general, gadodiamide and gadoversetamide are more likely to produce a clinically significant interference than gadopentetate dimeglumine and gadoteridol. Likewise, certain analytic methods are more prone to interference, while others not affected.

Evaluation of a new point of care automated complete blood count (CBC) analyzer in various clinical settings.

BACKGROUND WBC counts and differentials are currently performed on complex analyzers in either central or satellite laboratories. Rapid and easy to use point of care (POC) CBC testing can benefit certain outpatient clinical settings, where the greatest clinical need has been demonstrated. METHODS We evaluated a new POC CBC analyzer Chempaq XBC (Chempaq A/S, Denmark) for hemoglobin, leukocyte counts and 3-part differentials and compared the results with established laboratory based Beckman Coulter LH750 analyzers. The performance of these POC analyzers was tested at multiple clinic locations as a part of regular care on both venous and finger stick blood samples. RESULTS Method validation parameters including precision, accuracy and linearity studies are within the acceptable limits between POC and lab based analyzers. Method comparison studies at various locations showed good correlation at various clinical settings including ER, primary care, Ob/Gyn, ICU, Pedi clinic, Hematology-Oncology clinics, and in-patient wards in venous blood samples. In addition, at the hematology-oncology clinic, the comparisons of venous as well as finger stick blood sample analyses showed good correlation. CONCLUSION The Chempaq XBC analyzer provides accurate hematologic results that can facilitate rapid quantitative assessment of CBC parameters and thus is clinically relevant, especially in outreach clinic settings and in critically ill patients.

Rapid liquid chromatography/tandem mass spectrometer (LCMS) method for clozapine and its metabolite N-desmethyl clozapine (norclozapine) in human serum.

Clozapine is indicated for the treatment of schizophrenia and related psychotic disorders. Several methods have been developed for monitoring Clozapine levels; however, they possess limited specificity and are often laborious. This study describes a simple liquid chromatography/tandem mass spectrometer (LCMS) method in human serum. The ion transitions monitored were m/z 327, 270, 296 for Clozapine, m/z 313, 192, 227 for Norclozapine and m/z 328, 271 for Loxapine. The assay is linear (25–1000 ng/ml) and showed a good correlation (r=0.98) within the analytical range of 79–1210 ng/ml in human serum. This assay is highly specific and sensitive for the simultaneous measurements of Clozapine and Norclozapine. The simplification of this assay makes it ideal for high throughput analyses of the patient samples in a routine clinical laboratory staffed with general medical technologists. J. Clin. Lab. Anal. 23:394–398, 2009.

Reducing analytical variation between point-of-care and laboratory HbA1c testing

Point‐of‐care (POC) HbA1c testing allows for timely treatment changes, improved glycemic control, and patient and provider satisfaction. Substantial variation between POC and laboratory HbA1c results has been reported. At our university hospital diabetes clinic, we observed significant negative bias in HbA1c with the DCA Vantage™ (Siemens Healthcare Diagnostics, Tarrytown, NY, USA) compared with the Tosoh G8 HPLC laboratory analyzer (Tosoh Bioscience, San Francisco, CA, USA). This led us to systematically analyze the bias with the goal of recalibrating the DCA to minimize bias.

Performance of rapid SOFIA Influenza A+B test compared to Luminex x-TAG respiratory viral panel assay in the diagnosis of influenza A, B, and subtype H3

Influenza is an acute respiratory illness caused by influenza A or B viruses that occur in outbreaks, mainly during the winter season. Rapid laboratory diagnosis of influenza can help guide the clinical management of suspected patients effectively. Clinical sensitivities and specificities of the rapid influenza diagnostic tests have varied considerably in the literature. Most of these studies are evaluated using previously frozen or stored specimens that had previously tested positive. This study compares the performance of the rapid SOFIA Influenza A+B test to nucleic acid multiplex test x-TAG respiratory viral panel (RVP) assay in freshly collected nasal aspirates and measured simultaneously by both assays. Retrospective data from 1649 nasal aspirates (September 2014 to May 2015) collected from adults as well as from children tested simultaneously by both rapid SOFIA Influenza A+B FIA immunofluorescence (Quidel, San Diego, CA) and qualitative nucleic acid multiplex RVP assay X-TAG Luminex technology (Luminex, Austin, Texas, USA) were analyzed. Concordance, and analytical sensitivity and specificity were evaluated for influenza A, subtypes H1 and H3, and influenza B. Prevalence for influenza A by RVP was 15%, for subtype H3 it was 11.2%, and for influenza B, 2.9%. None of the aspirates were positive for influenza A subtype H1. SOFIA Influenza rapid test demonstrated good specificity and low sensitivity compared with a nucleic acid test for influenza A, subtype H3, and for influenza B. SOFIA Influenza A + B test performed well in providing a rapid diagnosis, however, confirmatory molecular testing is recommended for negative test results. Re-evaluation of test performance should be periodically carried out during outbreaks with the emergence and circulation of new influenza strains.