Sample clinical

Selected Examples of the Application of UV/Vis Molecular Absorption to the Analysis of Clinical Samples... 

Clinical Applications UV/Vis molecular absorption is one of the most commonly employed techniques for the analysis of clinical samples, several examples of which are listed in Table 10.7. 

The analysis of clinical samples is often complicated by the complexity of the sample matrix, which may contribute a significant background absorption at the desired wavelength. The determination of serum barbiturates provides one example of how this problem is overcome. The barbiturates are extracted from a sample of serum with CHCI3, and extracted from the CHCI3 into 0.45 M NaOH (pH 13). The absorbance of the aqueous extract is measured at 260 nm and includes contributions from the barbiturates as well as other components extracted from the serum sample. The pH of the sample is then lowered to approximately 10 by adding NH4CI, and the absorbance remeasured. Since the barbiturates do not absorb at this pH, the absorbance at pH 10 is used to correct the absorbance at pH 13 thus... 

Quantitative voltammetry has been applied to a wide variety of sample types, including environmental samples, clinical samples, pharmaceutical formulations, steels, gasoline, and oil. 

Miscellaneous Samples Besides environmental and clinical samples, differential pulse polarography and stripping voltammetry have been used for the analysis of trace metals in other samples, including food, steels and other alloys, gasoline, gunpowder residues, and pharmaceuticals. Voltammetry is also an important tool for... 

Flow injection analysis has been applied to a wide variety of samples, including environmental, clinical, agricultural, industrial, and pharmaceutical samples. The majority of analyses to date involve environmental and clinical samples, which is the focus of this section. 

Flow injection analysis has also found numerous applications in the analysis of clinical samples, using both enzymatic and nonenzymatic methods. A list of selected examples is given in Table 13.3. 

The INDA actually is a request for a Claimed Investigational Exemption to allow the transport of clinical samples of a nonapproved dmg into interstate commerce for the testing in human subjects. 

Biopolymers are employed in many immunological techniques, including the analysis of food, clinical samples, pesticides, and in other areas of analytical chemistry. Immunoassays (qv) are specific, sensitive, relatively easy to perform, and usually inexpensive. For repetitive analyses, immunoassays compare very favorably with many conventional methods in terms of both sensitivity and limits of detection. 

FIGURE 2.7 SEC elution profiles of dextran in clinical samples, serum ( ) and urine ( ). The first peak represent dextran and the second peak inulin (used as a reference for clearance). The content of carbohydrates was determined in collected fractions with the anthrone method. [Reproduced from Hagel ef of. (1993), with permission.]... 

Viruses that contain amino acid substitutions in the sialidase that impart resistance to the developed inhibitors have been isolated from serial passage of virus in the presence of drug in cell culture and from the clinical setting (reviewed in McKimm-Breschkin 2000 Zambon and Hayden 2001 Cinatl et al. 2007a Reece 2007). In addition, influenza B virus variants with reduced drug sensitivity have been isolated from previously untreated patients (Hurt et al. 2006 Hatakeyama et al. 2007). The types of mutations that are observed are sub-type specific. The mutations present in variants isolated from clinical samples are shown in Table 1, and their locations within the sialidase active site are shown diagrammatically in Fig. 9. 

Cornelis R (1996) Involvement of analytical chemistry in chemical speciation of metals in clinical samples. Ann Clin Lab Sd 26 252-263. 

Cornelis R, De Kimpe J, and Zhang X (1998) Trace elements in clinical samples revisited -speciation is knocking at the door. Sample preparation, separation of the spedes and measurement methods. Spectrochim Acta 536 187-196. 

Sheehan TM, Halls DJ 1999) Measurement of selenium in clinical samples. Ann Clin Bio-chem 36 301-315. 

Laboratory identification of Candida in clinical samples must be performed to the species level whenever possible, as Candida species differ considerably in their susceptibility to antifungal agents. 

The reference standards are used to quantitate the standards that are employed in the kits to generate the standard curves. The kit standards are recombinant single-stranded DNA molecules that are added to either negative serum or plasma at known concentrations. Because the standard curve is not constructed with reference standards, Chiron initially chose to use the term equivalent to describe the units of nucleic acid quantitation in clinical samples. An equivalent was defined as the amount of nucleic acid in a clinical sample that gave a signal equal to one molecule of the reference standard nucleic acid. The term copy rather than equivalent is used to describe the units of nucleic acid quantitation in the HIV-1 bDNA assay. The terms are now used interchangeably. 

In bDNA the number of target molecules is not altered. The signal of direct hybridization rather than the nucleic acid sequence itself is amplified and thus is directly proportional to the amount of target sequence present in the clinical sample. Both RNA and DNA sequences can be measured directly in clinical specimens, and there is no need to transcribe RNA into cDNA as there is with PCR. 

False-positive results with bDNA have been observed with proficiency testing specimens for HTV-1 in the College of American Pathologists HIV-1 viral load survey and HCV in the viral quality control program administered by the Netherlands Red Cross. The reason for the false-positive results with these proficiency testing specimens is not known but may be sample matrix effects. The extent to which this problem occurs with clinical samples has not been determined. However, both the HIV-1 and HCV bDNA assays were designed to have a false-positive rate of 5%. 

Pawlotsky, J.-M., et al. (1997). What technique should be used for routine detection and quantification of HBV DNA in clinical samples J. Virol. Methods 65,245-253. 

The use of the in vivo labeling methods described above is limited by the fact that the sample must be grown in the presence of the labeling isotopes. In many cases, it is not feasible to perform in vivo metabolic labeling. For example, for human clinical samples it is not possible to perform in vivo labeling and yet it is highly desirable to obtain accurate quantitative information on protein expression levels within these samples. Therefore, robust methods are needed for quantitation of protein levels in the absence of in vivo labeling with isotopes. 

A variety of commercial kits and automated systems are available to test the abilities of bacteria to assimilate, ferment, decarboxylate, or cleave selected organic compounds.46 Their reliability for species identification is usually greater with cultures from clinical samples, where a limited number of bacteria are commonly encountered, and less with environmental soil and water samples, where a great many uncommon or previously unidentified species not in the database are likely to be present.29,45 Additional tests beyond those found in the commercial kits may be necessary for example, the hydrolysis of various nitriles and amides is useful for identifying Rhodococcus spp.47 Some commercial kits for clinical use feature antimicrobial susceptibility testing.21... 

In bacterial cells, marker compounds are present at the part per hundred to part per thousand level. In environmental samples, which represent a complex mixture of components, such markers are often present at the part per ten thousand to part per hundred thousand level. In certain clinical samples, in some instances, these markers may be present as low as parts per... 

Clark, B.J., Hamdi, A., Berrisford, R.G., Sahanathan, S., Meams, AJ. (1991). Reversed-phase and chiral high-performance liquid chromatographic assay of hupivacaine and its enantiomers in clinical samples after continuous extraplural infusion. J. Chromatogr. 553,383-390. 

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