Biomedical subjects
Publications and source records attributed to Trefor N Higgins.
Everyone has been a newborn, and everyone's mother has been pregnant. Despite the commonality of these events, medical care and the clinical chemistry laboratory's role in it have changed remarkably over the last 50 years. This review is a historical overview of clinical chemistry testing that is related to pregnancy and the newborn period.
OBJECTIVE: To evaluate if peak characteristics, the retention time, and percentage of total hemoglobin of an unknown peak on the Bio-Rad VARIANT II Hb A1c method may be used to establish a tentative identification of hemoglobin variants. METHOD: The peak characteristics, retention time, and percentage of total hemoglobin obtained on abnormal peaks found on the Bio-Rad VARIANT II Hb A1c method were tabulated and evaluated against the identification of the hemoglobin variant established by the Bio-Rad beta thalassemia HPLC method and hemoglobin electrophoresis at both acid and alkaline pH. RESULTS: Some hemoglobin variants show specific peak characteristics, retention times, and percentage of total hemoglobin on the Bio-Rad VARIANT II Hb A1c method that allows for tentative identification of the hemoglobin variant. The retention times and percentage of hemoglobin variant for the common hemoglobin variants E, D, S, and C obtained on the Bio-Rad VARIANT II Hb A1c method are tabulated below. CONCLUSION: Peak characteristics, retention times, and percentage of hemoglobin variant may be used to establish the presence of a hemoglobin variant and to provide a tentative identification of some hemoglobin variants on the Bio-Rad VARIANT II Hb A1c method.
OBJECTIVES: : The aims of this study were to improve the resolution of albumin variants (bisalbumins, especially albumin Naskapi) from albumin in commercial serum protein electrophoresis systems; to compare the separation of bisalbumin from albumin on these improved methods against the recognized gold standard of capillary electrophoresis; and to investigate the presence of albumin variants in urine. DESIGN AND METHODS: : Electrophoresis was performed using the Sebia Hydrasys 15/30 beta1beta2 system, as well as modified methods on the Sebia Hydrasys HR and the Beckman Paragon systems. The interpretation of electrophoretic gels was performed by manual visualization and densitometric scanning. Serum samples were also analyzed using capillary electrophoresis at Sebia Electrophoresé located in Paris, France. Urine samples were concentrated using Vivaproducts concentration tubes and were electrophoresed using the Sebia Hydrasys HR system. RESULTS: : Representative gels and scans of serum samples demonstrate the improved resolution of modified electrophoresis methods compared to routine methods. The raw data from the gels and scans were compiled to calculate concordance and discordance for each method. DISCUSSION: : The various commercial serum protein electrophoresis systems showed improved resolution using the modified methods. In comparison with capillary electrophoresis, the modified Sebia Hydrasys HR and Beckman Paragon methods using visualization demonstrated 100% concordance and thus performed equally as well as the gold standard. Urine studies found that variant albumins are also excreted in the urine in the same 50-50 ratio as that found in the serum.
BACKGROUND: Results on sera and calibrators vary 1.4- to 2.3-fold among commercial human chorionic gonadotropin (hCG) assays. The relative contributions of calibrators, standards, hCG charge isoforms, and major structural variants to this variation have not been quantified. METHODS: Purified hCG was separated by isoelectric focusing into four fractions with pI ranges of 3-4, 4-5, 5-6, and 6-7. These four fractions together with pure hCG, hyperglycosylated hCG, hCG beta-subunit (hCGb), nicked hCG, and hCGb core fragment (hCGbcf) were tested in nine commonly used commercial serum assays for hCG. The compositions of pure hCG preparations, standards, and commercial hCG preparations were determined by immunoassay. RESULTS: The three pure hCG preparations and the four hCG charge isoforms each showed parallel responses in the nine commercial hCG assays. Although wide variations were found in the detection of hCG structural variants by the nine assays (range for hyperglycosylated hCG, 468-1544 IU/L; for hCGb, 3187-5535 IU/L; for nicked hCG, 2736-4240 IU/L; and for hCGbcf, <2-130 IU/L), this did not correlate with the between-method variation observed in results for the three pure hCG preparations. Commercial preparations of hCG and calibrators showed great variation in their content of hCG structural variants (from 34% to 100% intact hCG). CONCLUSIONS: Intermethod differences in hCG results were not explained by changes in responses attributable to hCG charge isoforms or to hCG structural variants, but wide variation was observed in concentrations of hCG structural variants in calibrators and in detection of these structural variants. Differences in assay specificity and in composition of the calibrators are the most likely sources of between-method variation.
INTRODUCTION: Differences in human chorionic gonadotropin (hCG) results obtained by seven different methods were documented by analyzing dilutions of the WHO 4th International Standard (IS) and a pregnant patient's serum. MATERIALS AND METHODS: Biases of +30.9 to -37.5% and +36.8 to -36.1% from the target concentration were found for the WHO 4th IS and patient sample dilutions, respectively. RESULTS: Imprecision was calculated from replicate measurements of hCG on the different sample dilutions. Imprecision ranged from 1.0% to 18.9% and 1.1% to 5.3% for the WHO 4th IS and patient sample dilutions, respectively. Using a maximum allowable error of 12.5% for hCG measurements, we found that two instruments were so biased that their hCG measurements could not be interchanged with hCG values produced by any of the other systems. DISCUSSION: It is ideal to use only one hCG methodology for the serial monitoring of hCG; otherwise, hCG methods should be carefully chosen to minimize inter-method bias.
OBJECTIVE: To compare lactate, bilirubin and Hemoglobin F concentrations obtained on ABL 700 series blood gas analyzers with those from laboratory methods. DESIGN AND METHOD: Pooled neonatal plasma, cord blood and adult plasma samples were used for comparison of bilirubin, hemoglobin F and lactate concentrations respectively. RESULTS: Results obtained on the ABL 700 series compared favorably (Deming regression slopes 0.97-1.13) with those from laboratory methods. For lactate ABL (y) = 1.13 Vitros (x) -0.43 with a CI (slope) of 1.10 to 1.16, CI (int) of -0.61 to -0.28. For hemoglobin F ABL(y) = 1.11 Variant (x) -8.0 with a CI (slope) of 0.88 to 1.33, CI (int) of -25.3 to 9.3. The three bilirubin comparisons are as follows: 1) Unistat (y) = 1.10 Vitros (x) -16.12 with CI (slope) of 1.06 to 1.14 and CI (int) of -25.3 to -6.9. 2), ABL (y) = 0.97 Vitros(x) -10.16 with CI (slope) of 0.94 to 1.00 and CI (int) of -17.6 to 2.73) Unistat (y) = 1.14 (x)-4.58 with CI (slope) of 1.09 to 1.18 and CI (int) of -13.6 to 4.5. CONCLUSION: The ABL 700 series gave comparable results for lactate, bilirubin and hemoglobin F with laboratory methods and may be used in patient care.