Evaluation of an adenosine deaminase (ADA) assay in serum, pleural, pericardial, peritoneal, and cerebrospinal fluids on the Roche cobas c501 analyzer.

OBJECTIVES: Adenosine deaminase (ADA) can be increased in various body fluids during infectious and inflammatory states. The objective of this study was to evaluate the performance characteristics of the Diazyme ADA assay for serum, pleural, pericardial, peritoneal, and cerebrospinal fluids using the Roche cobas c501 analyzer. METHODS: Accuracy, linearity, recovery, precision, sensitivity, specificity, reference interval, and stability studies were conducted. Potential interference of hyaluronidase and ultracentrifugation pre-treatment for viscosity on ADA concentrations were further evaluated. RESULTS: Assay method comparison to two separate external laboratories showed the following results (slope, intercept, %bias): serum (1.053, -0.478, 4.4 %); pleural (1.046, -1.41, 2.6 %). Accuracy (109.6 % recovery) was further demonstrated using a commercially available ADA reference material (BCR647). Linearity and spiked recovery studies showed percent recoveries ranging 94.3-109.3 %. Precision across all specimen types was ≤4.7 %CV. Interference was observed with increasing concentrations of various sources of conjugated and unconjugated bilirubin. Reference intervals were established for serum and pleural fluids, and previously published reference intervals were verified for pericardial, peritoneal, and cerebrospinal fluids. All specimen types were stable for 24 h ambient (8-25 °C), 1 week refrigerated (2-8 °C), and 1 month frozen (-20 °C). Of the two types of hyaluronidase evaluated, one showed positive interference for ADA (Sigma-Aldrich, H3506; 4.59 to 17.90 average % difference from baseline). Ultracentrifugation did not interfere with results (-2.32 to 0.87 average % difference from baseline). CONCLUSIONS: The Diazyme ADA assay was validated for use in our laboratory for all fluid types evaluated. Interference was observed with increasing concentrations of bilirubin and one source of hyaluronidase.

Plasma hemoglobin: A method comparison of six assays for hemoglobin and hemolysis index measurement.

INTRODUCTION: Plasma hemoglobin (Hb) is measured for assessment of in vivo and in vitro hemolysis. The objective of the present investigation was to conduct a method comparison of five quantitative and one semi-quantitative Hb and H-index (hemolysis index) assays to evaluate their performance measuring plasma Hb in clinical specimens. METHODS: One hundred and fourteen clinical specimens previously tested for plasma Hb using a laboratory-developed spectrophotometric assay were also tested for Hb using a HemoCue Plasma/Low Hb assay (azide methemoglobin), a laboratory-modified Pointe Scientific Hb assay (cyanmethemoglobin), tested for H-index measurements using a Roche cobas c501, an Abbott Architect c8000, and a semi-quantitative (binned) H-index measurement on a Beckman AU5800. The reference result was defined as the median Hb score (median of all Hb or H-index results). RESULTS: The laboratory-developed spectrophotometric Hb assay and Roche H-index methods mostly closely matched the median Hb score across all data, as well as for lower range median Hb score results ≤2.0 g/L. Two-way frequency table analysis using an Hb (or H-index) cutoff of 0.5 g/L (or 0.5 H-index units) was then performed to compare methods to the median Hb score cutoff. The Beckman method had the highest accuracy at this cutoff, the Roche and Abbott methods had the highest positive predictive value (PPV), and the Beckman, HemoCue, and Pointe methods had the highest negative predictive value (NPV). CONCLUSIONS: Plasma Hb and H-index results vary by method. Laboratories should evaluate the performance characteristics of their respective assays when considering adoption of spectrophotometric or chemical methods for plasma Hb assessment.

The availability of community ties predicts likelihood of peer referral for mammography: geographic constraints on viral marketing.

Engaging social networks to encourage preventive health behavior offers a supplement to conventional mass media campaigns and yet we do not fully understand the conditions that facilitate or hamper such interpersonal diffusion. One set of factors that should affect the diffusion of health campaign information involves a person's community. Variables describing geographic communities should predict the likelihood of residents accepting campaign invitations to pass along information to friends, family, and others. We investigate two aspects of a community--the availability of community ties and residential stability--as potential influences on diffusion of publicly-funded breast cancer screening in the United States in 2008-2009. In a survey study of 1515 participants living in 91 zip codes across the State of Minnesota, USA, we focus on the extent to which women refer others when given the opportunity to nominate family, friends, and peers to receive free mammograms. We predicted nomination tendency for a particular zip code would be a function of available community ties, measured as religious congregation density in that zip code, and also expected the predictive power of available ties would be greatest in communities with relatively high residential stability (meaning lower turnover in home residence). Results support our hypotheses. Congregation density positively predicted nomination tendency both in bivariate analysis and in Tobit regression models, and was most predictive in zip codes above the median in residential stability. We conclude that having a local infrastructure of social ties available in a community predicts the diffusion of available health care services in that community.