Serum reference material

Veillon C, Patterson KY and Reamer DC (1984) Preparation of a bovine serum pool for tr ace element analysis. In Wole WR. ed. Biological Reference Materials, ppihy-iyy. John Wiley Sons. 

Versieck J, Vanballenberghe L, de Kesel A, Baeck N, Steyart H, Byrne AR and Sunderman FW Jr. (1988) Certification of a second-generation biological reference material (freeze dried human serum) for trace element determinations. Anal Chim Acta 204 63-75. 

Byrne AR, and Versieck J (1990) Vanadium determination at the ultratrace level in biological reference materials and serum by radiochemical neutron activation analysis. Biol Trace Elem Res 27 529-540. 

Cali JP, Mandel J, Moore L, and Young DS (1972) A Referee Method for the Determination of Calcium in Serum Standard Reference Materials. NBS Spec Publ 260-36. National Bureau of Standards, Washington, DC. 

The first four materials (IRMM/IFCC-452, 453, 454, 455) are expected to be released during 2000. Projects on the certification of reference materials for cardiac marker (myoglobin) and total protein concentration in serum are under discussion. Even so the number of available CRMs for clinical chemistry and occupational toxicology is still limited. This has to do with the complexity of physiological compounds (e.g. proteins), the instabihty (e.g. enzymes), or the volatility (e.g. solvents). 

There are no special problems with the reconstitution or handling of these kinds of materials for electrolytes. The concentration of electrolytes is high, and no contamination problems are to be expected. Many commercial suppliers deliver reference materials for electrolytes in serum and urine. 

Solvents or their metabolites are commonly determined by GC (Tokunaga et al. 1974) or GC-MS. In spite of the high importance of exposure to solvents, and the great number of determinations performed worldwide, reference materials for solvents in serum or urine are virtually non-existent. There are a number of reference materials used in occupational hygiene, for example the ethanol in water standard from NIST (SRM 1828a) is commonly used in the clinical laboratory. 

Even though PAHs are commonly determined by GC or HPLC, there are no matrix reference materials for PAHs in urine or serum. A number of reference materials certified for PAHs in animal tissue are available, but they are intended for environmental applications, see Section 3.4. 

Many pesticides are neurotoxicants poisoning the nervous system. A number of pesticides are acetyl cholinesterase inhibitors (Serat and Mengle 1973). Generally, pesticides determination has been performed by GC since the 1960 s (Morrison and Durham 1971 Fournier et al. 1978). There are no reference materials for pesticides in urine or serum, although as with PAHs there are a number biological matrices certified for the content of various pesticides available for environmental food and agriculture analysis and which may have some application in clinical chemistry. 

Most used methods are spectrophotometry and immunochemistry, in dedicated laboratories ultracentrifugation. A handbook on this material has been written by Rifai et al. (1997). Certified reference materials for the determination of lipids in serum are provided by NIST. 

The application of PSA measurements for clinical monitoring of prostatic carcinoma requires fine tuning of PSA assays. One important aspect of this tuning is to have well-defined standards (primary calibrators). Calibrators or primary reference materials consisting of PSA complexed with ACT have been prepared and are available to sponsors of commercial immunoassays. As a result of this, some sponsors have studied calibration stability and have shown that calibration did not change within 14 to 90 days. Primary references of 90 percent PSA-ACT and 10 percent f-PS A have been shown to minimize differences in PSA measurements between different assays [NCCLS Document—Primary Reference Preparations Used to Standardize Calibration of Immunochemical Assays for Serum Prostate... 

To give an example, if a producer prepares 4000 vials from a batch of human serum, to be used as certified reference material for cholesterol measurements, it is neither practical nor realistic to measure the cholesterol content in all the 4000 vials. The measurements will be performed only on a number of vials. This will be discussed in more detail below. 

Accurate determination of the biological important element, selenium, in blood serum by isotope dilution analysis using ICP-QMS with octopole collision cell (Agilent 7500ce, Tokio, Japan) is described by Schaumloffel and coworkers.55 A recovery of selenium from human serum reference material was only 78 % when hydrogen was applied as collision gas but 96.7 % using xenon as a non-reactive collision gas to eliminate isobaric interferences. A detection limit of 3.3p,gl-1 was achieved.55... 

CDC anticipated two problems with providing trace-ability to clinical laboratories. First, matrix effects limit the use of processed serum-based reference materials in standardization. One solution is to use fresh serum specimens for accuracy transfer and method comparisons. Second, CDC realized it could not standardize an esti-... 

The most extensive effort involves quality assurance. CDC provides common quality control (QC) materials and all members use standardized QC procedures. In addition, CDC regularly surveys the CRMLN laboratories to ensure they meet the required criteria. Initially, surveys were conducted monthly however, as the laboratories gained experience and performance improved, the survey schedule was changed to bimonthly. These surveys use CDC frozen serum secondary reference materials that have been prepared using NCCLS C37-A protocol [28], TC surveys include three levels analyzed in duplicate in two runs. HDLC surveys include four levels analyzed in duplicate in four runs. As an additional check on the quantitative step of the HDLC method, a low-total cholesterol material with cholesterol concentration <100 mg/dl is added to the TC survey. LDLC surveys include four levels analyzed in quadruplicate in four runs. 

NCCLS (1999) Preparation and validation of commutable frozen human serum pools as secondary reference materials for cholesterol measurement procedures. NCCLS, Wayne, Pa. NCCLS document C37-A... 

Nevertheless, manufacturers are interested in the further development of reference materials and reference measurement procedures suited for application in human serum for medical purposes. Therefore, industry appreciates the efforts started by the Joint Committee of Trace-ability and Laboratory Medicine (JCTLM), an initiative supported by the Bureau International des Poids et Mesures (BIPM) and the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) in order to develop suitable reference materials and measurement procedures, as well as to collect information on the activities of reference laboratories. In view of the limited resources and large efforts connected with these activities, clear priorities need to be set. Projects need to take into account the clinical importance of the analyte, consider the technical difficulties that must be overcome, and, most importantly, decide whether improvement of the metrological side is reflected in a gain of medically relevant information. 

Abstract Some problems arising in the establishment of the traceability of the certified reference material (CRM) CZ 6007a (total protein, creatinine and stress indicators) are discussed. Bovine serum albumin is recommended as a calibration standard for total protein determination... 

A reference material (RM) for traceability of total protein in human urine does not exist. The control materials used in clinical laboratories for calibration purposes are not unified. Some laboratories use bovine serum albumin as a calibration material (URINE-CHIMIE BIOTROL) [5], whereas others use a mixture of human serum albumin (70%) and globulin (30%) (LYPHOCHECK Quantitative Urine Control, BIO-RAD) [6]. The use of various protein calibration standards yields various results of... 

In our experiments crystalline bovine serum albumin from Fluka, cat.no. 05470, (FLUKA albumin) was used for calibration and traceability purposes. The Fluka product was tested for traceability against the National Institute of Standards and Technology (NIST), USA Standard Reference Material (SRM) 927c (Total Protein Standard) bovine serum albumin (NIST albumin). Two different statistical techniques were used to evaluate traceability of the FFUKA albumin to the NIST albumin. 

Method-dependent measurements can be grouped by sector. For example, in the clinical fields there are cases where some higher order reference materials are required for IVD methods, such as for determination of glucose in human serum. It is also required of reference laboratories in specific measurement methods. These issues are now under the responsibility of JCTLM (Joint Committee on the Traceability of Laboratory Medicine of CCQM). CENAM has developed a reference material for glucose and cholesterol determination in human serum, and certified by IDMS, which is under review by JCTLM for the use by reference laboratories in any country applying a reference method. 

NIST methods and Reference Materials Development of reference methods and reference materials for the determination of hormones in human serum... 

The National Institute of Standards and Technology, Analytical chemistry division, Development of Reference Methods and Reference Materials for the Determination of Hormones in Human Serum. http //www.nist.gov/mml/analyticaForganic/hormonesinserum.cfm... 

Production of a human serum reference material with well-known concentrations of cortisol. The low level ampoules should contain approximately 100 ng/ml cortisol, whereas the high level ampoules should contain 300 ng/ml cortisol, respectively. 

In the past few years great technical progress has been made in lyophiliza-tion. Lyophilization and ampouling under nitrogen also overcomes the problems of destructive postal delays. Therefore, the BCR has decided to prepare the reference material as lyophilized human serum. Some people believe that lyophilization alters the properties of the serum to such an extent that problems can arise in matrix-dependent measuring techniques such as radioimmunoassay (RIA) and competitive protein binding (CPB) (Menson and Adams, 1977 Fraser et al., 1978 DiSilvio, 1979). Indeed, before the lyophilized material can be used it should be checked to determine whether the material can be satisfactorily reconstituted and whether it can be assayed by the different techniques currently in use in clinical laboratories. 

The problem of developing accurate data for chromium in biological samples is further complicated by the lack of Standard Reference Materials (SRM). Only recently have chromium certified materials, such as brewer s yeast (SRM-1569), bovine liver (SRM-1577), human serum (SRM-909), urine (SRM-2670), orchard leaves (SRM-1571), spinach leaves (SRM-1570), pine needles (SRM-1575), oyster tissue (SRM-1566), and tomato leaves (SRM-1573) been issued by the National Institute of Standards and Technology (formerly the National Bureau of Standards). Because of the lack of SRMs, the less recent data should be interpreted with caution (EPA 1984a), unless the data are verified by interlaboratory studies. 

Freeze-dried materials for urine samples are nearly as commonplace as serum samples. These materials possess long-term stability and are used for the determination of pentachlorophenol [25] and metals such as Pb [26] and Cd [27], among others. In most cases, the results for the freeze-dried reference material are indistinguishable from those for fresh urine. 

---