Urine analyzer, automated

In addition to the automated devices and processing units that were developed primarily to automate chemistry and immunoassay that are described above, a variety of other instruments and processes have been automiated and used in the clinical laboratory. They include urine analyzers, flow cytometers, hematology cell counters, nucleic add analyzers, microtiter plate systems, point-of-care analyzers, and remotely located systems. 

Blood and urine are most often analyzed for alcohol by headspace gas chromatography (qv) using an internal standard, eg, 1-propanol. Assays are straightforward and lend themselves to automation (see Automated instrumentation). Urine samples are collected as a voided specimen, ie, subjects must void their bladders, wait about 20 minutes, and then provide the urine sample. Voided urine samples provide the most accurate deterrnination of blood alcohol concentrations. Voided urine alcohol concentrations are divided by a factor of 1.3 to determine the equivalent blood alcohol concentration. The 1.3 value is used because urine has approximately one-third more water in it than blood and, at equiUbrium, there is about one-third more alcohol in the urine as in the blood. 

Blood samples were centrifuged at 1000 x g for 20 min at 0-4°. Ionized calcium levels were immediately determined in serum and urine samples using a calcium ion-selective electrode (Ionetics, Inc., Costa Mesa, CA) urine volumes were recorded. The remaining serum and urine were aliquoted for various analyses and stored at -40°. Serum insulin was analysed by radioimmunoassay (Amersham Corp., Arlington Heights, IL). Serum levels of total calcium, phosphorus and creatinine as well as urine creatinine were determined by colorimetric procedures using an automated analyzer (Centrifichem, Baker Instruments Corp., Pleasantville, NY). Glomerular filtration rates (GFR) were calculated from serum and urine creatinine data GFR = urine creatinine/serum creatinine. 

A study involving twenty-six laboratories was carried out to assess the quality of amino acid analysis, using samples of urine and lyophilized plasma. Coefficients of variation ranged from 13% for glycine to 65% for methionine. Automated IEC followed by ninhy-drin detection (37) seemed to perform better than other methods however, there was no clearly superior method and no analyzer clearly outperformed the others. This seems to point to the importance of personal proficiency and expertise in the performance of such analyses137. 

Alarcon (1976) developed a method for quantifying 3-hydroxypropylmercapturic acid (MCA), a known metabolite of acrolein, in urine. This method involves acidification of the urine to convert MCA to S - (3 - hydroxypropyl) - L - cysteine. The amount of S - (3 - hydroxypropyl) - L - cysteine can then be quantitated using an automated amino acid analyzer. 

The glucose oxidase method (used in the dipsticks and by many automated analyzers) can show a false positive result in some species (e.g, dog, mouse) with high urinary ascorbate levels or in urine contaminated with hypochlorite (bleach) used as a disinfectant (Finco 1997 Loeb and Quimby 1999). 

Many of the same analytical principles are used for the quantitation of serum and urine constituents, but it is more difficult to automate testing of urine than serum, because the broad range of concentrations of many urine constituents requires a low limit of detection to measure low concentrations, and expanded linearity to permit measurements of high concentrations without dilution. This requirement, together with the relatively low demand for urine tests compared with that for serum tests, has restricted the development of analyzers designed specifically for urine constituents. Nevertheless, selected urine analyses are performed on the available analyzers in some institutions. ... 

Lott JA, Johnson WR, Luke KE. Evaluation of an automated urine chemistry reagent-strip analyzer. J Clin Lab Anal 1995 9 212-17. 

Kasdan HL, Ashe M, Chapoulaud E, Dougherty WM, Halby S, Tindel JR. Comparison of pathological cast analytical performance and flagging of automated urine sediment analyzers a new flow imaging system versus flow cytometry. Chn Chem 2003 49 A160. 

Albumin in the urine sample forms an insoluble complex with antibodies to human albumin. PEG accelerates complex formation. The turbidity caused by the complexes is measured by a spectrophotometer at 340run and is a measure of albumin concentration. The background absorbance of the initial urine sample is subtracted automatically. This method is simple and less expensive than RIA, and rapid analysis of large numbers of samples is possible. The assays may be performed as either kinetic or equilibrium reactions. Kits are commer-cially available for use on automated analyzers (Roche Diagnostics). 

Pyridinium Cross-links (Deoxypyridinoline and Pyridi-noline). DPD and PYD were originally measured by HPLC (see Table 49-5). Today, DPD is measured primarily by immunoassay using automated analyzers (EIA with chemiluminescence detection and ICMA) or manual ELISA. Unlike most HPLC methods, which measure total DPD and total PYD, the immunoassays for DPD or DPD/PYD measure primarily free but not peptide-bound forms. In urine, approximately 40% of the PYD and DPD is free and 60% is protein-bound. 

The first fully automated instrument for chemical analysis (the Technicon Auto Analyzer ) appeared on the market in 1957. This instrument was designed to fulfill the needs of clinical laboratories, where blood and urine samples are routinely analyzed for a dozen or more chemical species. The number of such analyses demanded by modern medicine is enormous, so it is necessary to keep their cost at a reasonable level. These two considerations motivated the development of analytical. systems that perform several analyses simultaneously with a minimum input of human labor. The use of automatic instruments has spread from clinical laboratories to laboratories for the control of industrial processes and the routine determination of a wide spectrum of species in air, water, soils, and pharmaceutical and... 

The future of ISEs in the clinical chemistry instrumentation is quite exciting. As described in subsequent sections of this article, the coupling of enzyme and immunological reagents to ISE detectors to form bioelectrode systems appears to offer manufacturers a new approach toward the detection of metabolites such as creatinine and urea directly in blood and urine samples. Ultimately, such biosensors will be placed into complete electrode-based automated clinical analyzers. In addition, continued research on new membrane formulations, particularly liquid membrane ionophore systems, will result in the development of addition electrodes which can be incorporated into current analyzer systems to expand the electrolyte menu. Indeed, recent efforts have indicated that membranes selective fi)r bicarbonate (F5) and lithium (Z2) are likely additions in the near future. 

Table 1 lists several of the chemical determinations and the corresponding reactions utilized, which are available on automated clinical analyzers. With the exception of assays for various electrolytes, eg, Na+, K+, CT, and CC>2, determination is normally done by photometric means at wavelengths in the ultraviolet and visible regions. Other means of assay include fluorescence, radioisotopic assay, electrochemistry, etc. However, such detection methods are normally required only for the more difficult assays, particularly those of serum or urine constituents at concentrations below JTg L. These latter assays are discussed more fully in the literature (3,4). 

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