Effects of lyophilization of serum on the measurement of apolipoproteins A-I and B

1990 ◽  
Vol 36 (2) ◽  
pp. 366-369 ◽  
Author(s):  
S M Marcovina ◽  
J L Adolphson ◽  
M Parlavecchia ◽  
J J Albers
Keyword(s):  
Reference Materials ◽  
Apolipoprotein B ◽  
Matrix Effects ◽  
Reference Intervals ◽  
Assay Method ◽  
Common Reference ◽  
Apolipoprotein A ◽  
Quality Control Materials ◽  
Standardization Process ◽  
The Difference

Abstract A common accuracy-based standardization program is indispensable for establishing reference intervals for the clinical use of apolipoproteins. The development and distribution of reference materials and quality-control materials that do not exhibit matrix effects between methods is essential to the standardization process. We examined the suitability of lyophilized material as a common reference material for the measurement of apolipoproteins A-I and B. We determined values for apolipoproteins A-I and B in frozen and lyophilized serum pools, using different immunochemical approaches. We found little or no differences in apolipoprotein A-I values between frozen and lyophilized pools as determined by the different methods. In contrast, values for apolipoprotein B in lyophilized samples were consistently lower than those obtained for frozen samples. After adjusting for the effect of dilution due to reconstitution, the difference in the apolipoprotein B values for lyophilized as compared with frozen samples ranged from -26% to 4%, depending upon the assay method. Evidently, serum pools in lyophilized from are not a suitable matrix for reference materials for apolipoprotein B measurements but can be used for apolipoprotein A-I measurements.

Multicenter evaluation of the commutability of a potential reference material for harmonization of enzyme activities

2004 ◽  
Vol 42 (12) ◽  
Author(s):  
Volkher Scharnhorst ◽  
Joke Apperloo ◽  
Henk Baadenhuijsen ◽  
Huib L. Vader
Keyword(s):  
Reference Material ◽  
Reference Materials ◽  
Enzyme Activities ◽  
Regression Line ◽  
Reference Intervals ◽  
Correction Factors ◽  
Serum Samples ◽  
Field Methods ◽  
Common Reference ◽  
Fold Reduction

AbstractStandardization of laboratory results allows for the use of common reference intervals and can be achieved via calibration of field methods with secondary reference materials. These harmonization materials should be commutable, i.e., they produce identical numerical results independent of assay principle or platform. This study assessed the commutability of a cryolyoprotectant-containing harmonization material, obtained from the Dutch Foundation for Quality Assessment in Clinical Laboratories, that is intended to harmonize measurements of enzyme activities within the Dutch project “Calibration 2000”. The catalytic concentrations of alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, γ-glutamyltransferase and creatine kinase were analyzed in pooled patient sera and in the reference material in 14 laboratories. On liquid chemistry analyzers the harmonization material behaves like patient material. The enzyme activities measured in it fall on the regression lines calculated from activities measured in serum samples. For dry chemistry analyzers the activities of all enzymes measured in the harmonizator differ from the serum-based regression line. We show that this is due to the sucrose-containing cryolyoprotectant in the harmonization material. For each enzyme, correction factors were calculated that compensated for the bias and proved to be constant between reagent lots. Depending on the enzyme activity measured, application of these factors leads to 2- to 10-fold reduction of between-laboratory percentage coefficient of variation. Thus, additives to (potential) reference materials may alter their matrix in a way that interferes with analysis on certain test systems. The bias caused may be quantifiable and correctable. Establishment of correction factors leads to analytical uncertainties and costs. Therefore, matrix-based materials without additives should be selected as reference materials.

Proposal for guidelines to establish common biological reference intervals in large geographical areas for biochemical quantities measured frequently in serum and plasma

2004 ◽  
Vol 42 (7) ◽  
Author(s):  
Pål Rustad ◽  
Peter Felding ◽  
Ari Lahti
Keyword(s):  
Reference Materials ◽  
Standard Procedure ◽  
Reference Interval ◽  
Reference Intervals ◽  
Routine Method ◽  
Common Reference ◽  
Reference Samples ◽  
Project 2000

AbstractA suggestion for a standard procedure to establish biological reference intervals for biochemical quantities by a multicenter approach is presented. This procedure was developed for and used in the Nordic Reference Interval Project 2000 (NORIP). This project established biological reference intervals for 25 frequently requested biochemical quantities through cooperation of 102 Nordic laboratories. Each laboratory performed collection of reference samples and measurement using their routine methods. The bias of each routine method was eliminated by use of common reference materials measured in each of the participating laboratories.

scholarly journals Effect of Sex and Assay Method on Serum Concentrations of Growth Hormone in Patients with Acromegaly and in Healthy Controls

2006 ◽  
Vol 52 (3) ◽  
pp. 468-473 ◽  
Author(s):  
Helene Markkanen ◽  
Tuula Pekkarinen ◽  
Matti J Välimäki ◽  
Henrik Alfthan ◽  
Ritva Kauppinen-Mäkelin ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Tolerance Test ◽  
Reference Intervals ◽  
Assay Method ◽  
Specific Reference ◽  
Oral Glucose ◽  
Serum Samples ◽  
Serum Growth Hormone ◽  
The Difference

Abstract Background: Diagnosis and follow-up of acromegaly is based on measurements of serum growth hormone (GH) concentrations during an oral glucose tolerance test (OGTT). A nadir value <1 μg/L is commonly used to define a normal response, but some authors suggest lower cutoff values. Methods: To compare the results and subsequent patient classification obtained with 3 GH assays, we obtained basal serum samples from 78 apparently healthy adult controls (43 women and 35 men; median age, 32.5 years) and from 71 treated (44 women and 27 men; median age, 55.2 years) and 7 untreated acromegaly patients (4 women and 3 men; median age, 54.6 years), and OGTT was performed on all patients and on 72 of the 78 controls. GH was determined by 2 immunometric assays—a double monoclonal (AutoDELFIA; Wallac) and a monopolyclonal (Immulite 2000; DPC) assay—and in a limited set of samples by an RIA (Spectria RIA; Orion). Results: There was a strong correlation (r = 0.995; P <0.001) between the 2 immunometric methods, but the results obtained with the Immulite 2000 were, on average, 1.4-fold higher than those obtained with the AutoDELFIA. At concentrations around the cutoff (1 μg/L), however, the difference was ∼2-fold. Overall, the Orion RIA method also showed a good correlation (r = 0.951–0.959) with the other methods, but it did not measure concentrations <2 μg/L. Women had higher basal and OGTT nadir GH concentrations than men. Conclusion: Reference intervals should be determined separately for each method, and the need for establishing sex-specific reference values should be investigated.

scholarly journals Instability of Lipoprotein(a) in Plasma Stored at −70 °C

2001 ◽  
Vol 47 (9) ◽  
pp. 1673-1678 ◽  
Author(s):  
Josep M Simó ◽  
Jordi Camps ◽  
Elisabet Vilella ◽  
Federico Gómez ◽  
Antonio Paul ◽  
...  
Keyword(s):  
Southern Blotting ◽  
Epidemiologic Studies ◽  
Assay Method ◽  
Lipoprotein A ◽  
Apolipoprotein A ◽  
Initial Plasma ◽  
Sample Stability ◽  
Premature Myocardial Infarction ◽  
The Mean ◽  
The Difference

Abstract Background: There is considerable evidence to suggest that plasma lipoprotein(a) [Lp(a)] concentration is a cardiovascular risk factor. Confusing results in epidemiologic studies, however, suggest that the effects of storage should be further investigated. The influence of the assay method, the initial plasma Lp(a) concentration, and the apolipoprotein(a) [apo(a)] genotype are all factors that should be considered. Methods: Blood was obtained from 65 survivors of premature myocardial infarction and 95 age-matched controls. The plasma samples were stored in sterile conditions at −70 °C for 5 years in the presence of antioxidant and antiproteolytic substances. Plasma Lp(a) was measured by immunoturbidimetry, and apo(a) alleles were determined by pulsed-field gel electrophoresis and Southern blotting. Results: Plasma Lp(a) was significantly higher in patients. The mean kringle number for the smallest isoform was also lower in patients than in controls, but no differences were found in the distribution of the largest isoform. All patients and controls were heterozygotes. During storage, mean Lp(a) decreased significantly in samples from patients (−23%; P <0.001) but not in samples from controls (−9%; P, not significant). This was not related to the kringle number and was limited to samples with initial plasma Lp(a) concentrations between 41 and 345 mg/L. Conclusions: Plasma Lp(a) from patients is less stable than Lp(a) from controls, and the difference is not related to distribution of apo(a) genotypes but may be concentration-dependent. Differential sample stability may complicate the interpretation of several studies.

Standardization of the Immunochemical Determination of Apolipoproteins A-I and B: A Report on the International Federation of Clinical Chemistry Meeting on Standardization of Apolipoprotein A-I and B Measurements (Basis for Future Consensus), Vienna, Austria, April 18-19, 1989

1989 ◽  
Vol 35 (9) ◽  
pp. 2009-2015 ◽  
Author(s):  
Santica M Marcovina ◽  
John J Albers
Keyword(s):  
Therapeutic Response ◽  
Clinical Chemistry ◽  
Reference Intervals ◽  
Consensus Conference ◽  
International Federation ◽  
Clinical Use ◽  
Apolipoprotein A ◽  
Immunochemical Determination ◽  
Standardization Process

Abstract The central aim of standardization is to have accurate, reproducible apo A-I and B measurements for use in defining a person's risk for cardiovascular disease or in evaluating a therapeutic response. A common accuracy-based standardization program is indispensable in establishing international reference intervals for clinical use. It is therefore important that the standardization be implemented as soon as possible. Many problems of the standardization of apo A-I and B measurements have been presented and discussed in this meeting. Although immediate solutions to all the problems were not evident, following the recommendations from this meeting can significantly improve the standardization process. The next step is to determine uniform reference intervals, followed by a consensus conference on apolipoproteins to define the cutpoints (cutoff values) for clinical decisions.

Apolipoprotein(a), Fibrinopeptide A and Carotid Atherosclerosis in Middle-Aged Men

1994 ◽  
Vol 72 (04) ◽  
pp. 563-566 ◽  
Author(s):  
Tuomo Rankinen ◽  
Sari Väisänen ◽  
Michele Mercuri ◽  
Rainer Rauramaa
Keyword(s):  
Risk Factors ◽  
Cardiovascular Diseases ◽  
Carotid Atherosclerosis ◽  
Intima Media Thickness ◽  
Carotid Bifurcation ◽  
Carotid Intima Media Thickness ◽  
Fibrinopeptide A ◽  
Carotid Imt ◽  
Apolipoprotein A ◽  
The Difference

SummaryThe association between apolipoprotein(a) [apo(a)], fibrinogen, fibrinopeptide A (FPA) and carotid intima-media thickness (IMT) was analyzed in Eastern Finnish men aged 50 to 60 years. Apo(a) correlated directly with carotid bifurcation (r = 0.26, p = 0.001), but not with common carotid IMT. Men in the lowest quartile of apo(a) had thinner (p = 0.013) IMT in bifurcation [1.59 mm (95% Cl 1.49; 1.68)] compared to the men in the highest [1.91 mm (95% Cl 1.73; 2.09)] apo(a) quartile. The difference remained (p=0.038) after adjusting for confounders. Plasma fibrinogen was not related to carotid IMT, whereas FPA correlated with common carotid (r = 0.21, p = 0.016) and carotid bifurcation (r = 0.21, p = 0.018) IMT. These associations abolished after adjusting for the confounders. The data suggest that apo(a) associate with carotid atherosclerosis independent of other risk factors for ischemic cardiovascular diseases.

Bioanalytical method development and validation of simultaneous analysis of telmisartan and hydrochlorthiazide in human plasma using LC-MS/MS

2016 ◽  
Vol 5 (03) ◽  
pp. 4862 ◽  
Author(s):  
Mathew George* ◽  
Lincy Joseph ◽  
Arpit Kumar Jain ◽  
Anju V.
Keyword(s):  
Human Plasma ◽  
Retention Time ◽  
High Performance ◽  
Method Development ◽  
Matrix Effects ◽  
Solid Phase ◽  
Internal Standard ◽  
Assay Method ◽  
Buffer System ◽  
Internal Standards

A simple, sensitive, rapid and economic high performance thin layer chromatographic method and a mass spectroscopic assay method has been developed for the quantification of telmisartan and hydrochlorthiazide combination in human plasma. The internal standards and analytes were extracted from human plasma by solid-phase extraction with HLB Oasis1cc (30mg) catridges. The scanning and optimization for the samples are done using methanol: water (50:50). The samples were chromatographed using reverse phase chromatography with C-18 column of different manufacturers like Ascentis C18 (150×4. 6, 5µ) using the buffer system Acetonitrile: Buffer (80:20%v/v) which consist of 2±0. 1Mm ammonium format at a flow rate of 0. 7ml/min at a column oven temperature 35±10c. The internal standard used was hydrochlorthiazide13c1, d2 and telmisartand3. The extraction techniques include conditioning, loading, washing and elution, drying followed by reconstitution of the dried samples. The volume injected was 10µl with the retention time of 3-4 min for telmisartan, 1-2 min for hydrochlorthiazide and for the internal standards the retention time was 3-4 min for telmisartand3 and 1-2 min for hydrochlorthiazide c13d2. The rinsing solution was Acetonitrile: HPLC grade water in the ratio (50:50). The above developed method was validated using various parameters like selectivity and sensitivity, accuracy and precision, matrix effects, % recovery and various stability studies. The method was proved to be sensitive, accurate, precise and reproducible. The preparation showed high recovery for the quantitative determination of telmisartan and hydrochlorthiazide in human plasma.

EXPRESS: Method dependent variation in TSH and FT4 reference intervals in pregnancy: a systematic review

2021 ◽  
pp. 000456322110269
Author(s):  
O E Okosieme ◽  
Medha Agrawal ◽  
Danyal Usman ◽  
Carol Evans
Keyword(s):  
Systematic Review ◽  
Reference Interval ◽  
First Trimester ◽  
Reference Intervals ◽  
Assay Method ◽  
Specific Reference ◽  
Upper Limits ◽  
Wide Range ◽  
Assay Methods ◽  
In Pregnancy

Background: Gestational TSH and FT4 reference intervals may differ according to assay method but the extent of variation is unclear and has not been systematically evaluated. We conducted a systematic review of published studies on TSH and FT4 reference intervals in pregnancy. Our aim was to quantify method-related differences in gestation reference intervals, across four commonly used assay methods, Abbott, Beckman, Roche, and Siemens. Methods: We searched the literature for relevant studies, published between January 2000 and December 2020, in healthy pregnant women without thyroid antibodies or disease. For each study, we extracted trimester-specific reference intervals (2.5–97.5 percentiles) for TSH and FT4 as well as the manufacturer provided reference interval for the corresponding non-pregnant population. Results: TSH reference intervals showed a wide range of study-to-study differences with upper limits ranging from 2.33 to 8.30 mU/L. FT4 lower limits ranged from 4.40–13.93 pmol/L, with consistently lower reference intervals observed with the Beckman method. Differences between non-pregnant and first trimester reference intervals were highly variable, and for most studies the TSH upper limit in the first trimester could not be predicted or extrapolated from non-pregnant values. Conclusions: Our study confirms significant intra and inter-method disparities in gestational thyroid hormone reference intervals. The relationship between pregnant and non-pregnant values is inconsistent and does not support the existing practice in some laboratories of extrapolating gestation references from non-pregnant values. Laboratories should invest in deriving method-specific gestation reference intervals for their population.

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