Evaluation of a New Automated Routine Measurement for Serum Adjusted Ionized Calcium (at pH 7.4) in Patients Suspected of Calcium Metabolic Disease.

BACKGROUND: Total calcium is a less accurate test in predicting ionized calcium (Ca2+) in patients suspected of calcium metabolic disease. Nevertheless, total calcium continues to be used as routine measurement instead of adjusted Ca2+ (at pH 7.4). In the current study we evaluate a new multichannel instrument, the ISE Module E1200 for adjusted Ca2+ (at pH 7.4), containing three different ion-selective electrode (ISE) units. METHODS: Serum from 1350 patients was compared to the ABL835 flex and KoneLab. Total calcium was also evaluated on the Dimension Vista 1500 system. Correlations between instruments were assessed by Deming regression and degree of agreement by Cohen's kappa (κ). RESULTS: Analytical imprecisions for the three ISE units for adjusted Ca2+ (at pH 7.4) was between 0.36% and 2.52%, and for pH between 0.32% and 3.24%. Results were comparable for each ISE unit (r = 0.797-0.917; all P < 0.0001) and in high-throughput settings (r = 0.871; P < 0.0001). The degree of agreement between instruments was moderate to good (κ = 0.52-0.77). In contrast, there was a very poor agreement (κ = -0.14) for total calcium with discrepancy in 53.4% of the samples. CONCLUSIONS: The new ISE Module E1200 is comparable with the ABL835 flex and KoneLab 30i and therefore may be used for routine analysis of serum adjusted Ca2+ (at pH 7.4). The measured adjusted Ca2+ (at pH 7.4) was less comparable with very poor agreement to total calcium measured on the Dimension Vista 1500 system.

Evaluation of the HemoCue WBC DIFF in leukopenic patient samples.

BACKGROUND: White blood cell (WBC) counts are used to monitor bone marrow function and to screen for infections. The HemoCue WBC DIFF Point-Of-Care (POC) instrument classifies WBCs through cell image recognition. To evaluate its suitability for monitoring cancer patients, we examined its performance in samples from patient with leukopenia and in samples containing nRBC. METHODS: Sysmex samples with WBCs 0.05-3.40 × 109 /L were examined on the HemoCue WBC DIFF, and the correlations between the instruments were assessed by Deming regression for total WBC, neutrophils, and lymphocytes. The theoretical CV% (CVt), calculated from number of cells counted by the HemoCue WBC DIFF, was used to determine the statistical error of the WBC counts. The interference of nRBC was also evaluated. RESULTS: The counting variation was primarily the source of statistical error in the lower counts with an imprecision between 3.8-9.2% for total WBC (0.56-2.29 ×109 /L), 8.7-14.3% for neutrophils (0.36-1.33 ×109 /L) and 9.8-15.1% for lymphocytes (0.35-0.89 ×109 /L). The correlation coefficient was between 0.658 and 0.986-poorest for lymphocytes. The total WBC count on the HemoCue WBC DIFF was significantly increased in nRBC samples due to lymphocyte count overestimation, and not by other WBCs. CONCLUSIONS: The HemoCue WBC DIFF provided reliable and accurate counts of total WBC, neutrophil, and lymphocyte in leukopenic samples. Until POC instruments that can perform an accurate complete blood count are available, the HemoCue WBC DIFF can be used to assist physicians in making decisions in situations of postchemotherapy leukopenia and neutropenia.