Stand-alone automated solutions can enhance laboratory operations

Clinical laboratory automation has developed over the past decade as one means of consolidating testing, reducing costs, and improving the effectiveness of laboratory testing. Most of the developments have been aimed at core clinical laboratory operations, and have primarily addressed preanalytical and analytical processing of traditional specimens arriving in blood collection or similar aliquot tubes. Much less attention has been given to specialized applications such as processing specimens for urine toxicology, and only recently have vendors attacked the problems associated with sorting and maintaining the laboratory's inventory of specimens. This report highlights selected developments in these areas, describes one approach to cost-effective custom platform development, and discusses the advantages and pitfalls to solving problems with laboratory automation.

Evaluation of a newly available biochemical analyzer: the Olympus AU 600

The performance of the Olympus AU 600, a newly available open multiparametric analyzer, available for routine biochemical analysis of biological samples, was evaluated. The analytical and technical performance of the apparatus and the quality of the Olympus reagents were both examined in a single site study. Electrolyte concentrations were determined with patented ion-selective electrodes; substrate concentrations and enzyme activities were determined by spectrophotometric measurement after coloured reaction or UV detection-based-reactions. The protocol of the evaluation and the acceptability criteria were those recommended by the French Society for Clinical Biology. For the parameters studied, the upper limits of linearity were equal to or higher than those claimed by the manufacturer. The CV values for within-run and between-run precision were lower than the target values with few exceptions. The comparison study gave satisfactory results for most of the parameters. Only expected interferences occurred. In summary, the results obtained for the 25 parameters studied and the characteristics of the apparatus were satisfactory. The analyzer is rapid (800 to 1200 tests per hour) and easy to use. In addition, the analyzer complies with good analytical practice and its flexibility enables users to plan work according to local laboratory constraints.

A new method of quantitative fecal fat microscopy and its correlation with chemically measured fecal fat output

Fecal fat microscopy using the Sudan stain has suffered from a relative lack of specificity, and results are "qualitative." Therefore, we developed a quantitative fecal fat microscopic method with hopes of improving diagnostic accuracy. One hundred eighty patients with chronic diarrhea collected stools for 1 to 3 days, and fecal fat output was measured by a standard chemical method, and microscopy was performed by the old qualitative and new quantitative methods. There was a highly statistically significant linear correlation between quantitative fecal fat microscopy and chemically measured fecal fat output. The quantitative microscopic method had a sensitivity of 94% and a specificity of 95%; the traditional method had a sensitivity and specificity of 76% and 99%, respectively. Fecal fat Sudan microscopy performed by a dedicated approach to counting and size measurement of fat globules can yield a quantitative result that correlates well with chemically measured fecal fat output and has a high diagnostic accuracy.

Nonenzymatic elimination of ascorbic acid in clinical samples

OBJECTIVES

Ascorbic acid interferes significantly in the oxidative reaction of chromogenic reagents by peroxidase and hydrogen peroxide. Currently, ascorbate oxidase is commonly utilized for eliminating the interference of ascorbic acid in the oxidative colorimetric reaction. This enzyme, however, displays several disadvantages, such as high cost, variation from lot to lot, and low stability. We applied a series of commercially available and stable radicals (ascorbic acid quenchers [AAQs]) for nonenzymatic quenching of ascorbic acid in the uricase-based uric acid determination in serum and urine.

DESIGN AND METHODS

In order to evaluate the quenching activity of AAQs, a commercially available uric acid detection kit was used. TBA-80FR.NEO biochemical analyzer was utilized for the assay.

RESULTS

4-Hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical (AAQ-2) was the most effective ascorbic acid quencher among the four stable radicals, and the uric acid assay suffered no interference by AAQ-2. The ascorbic acid quenching ability of 2 mmol/L of AAQ-2 in reagent solution (reagent-I) was > or = 2 U/ml ascorbate oxidase in reagent solution.

CONCLUSIONS

AAQ-2 was proven to be a suitable quencher of ascorbic acid in clinical samples.

Assay of creatinine using the peroxidase activity of copper-creatinine complexes

OBJECTIVES

It was our goal to develop a urine dipstick that could measure creatinine with a peroxidase reaction. The simultaneous measurement of albumin and creatinine permits the estimation of the 24-h albumin excretion, an important value in judging existing or likely development of renal failure. A highly sensitive dye-binding dipstick method for albumin exists, and a suitable dipstick for the assay for urine creatinine is described here.

METHODS

Copper-creatinine and iron-creatinine complexes have peroxidase activity. With 3,3',5,5'-tetramethylbenzidine (TMB), and diisopropyl benzene dihydroperoxide (DBDH); the peroxidase activity of copper-creatinine and iron-creatinine complexes can be demonstrated. This reaction was used in the assay of urine creatinine either in solution or by a suitably impregnated urine dipstick.

RESULTS

Our method based on the peroxidase activity of the copper-creatinine complex has an analytical range for creatinine of 100 mg/L (0.884 mmol/L) to 3000 mg/L (26.52 mmol/L). The creatinine assay is free from most interfering compounds that may be present in urine. Hemoglobin is an interferent, and its effects can be reduced but not eliminated by the addition of 4-hydroxy-2-methyl quinoline. We do not recommend using the dipsticks when visible blood is present or if the dipstick blood test is positive. The copper-creatinine complex oxidizes ascorbic acid; however, we were able to modify the reaction conditions so that ascorbic acid at < 4.4 g/L does not interfere. We found good agreement on fresh urines between the creatinine dipstick results and those by a standard rate-Jaffe cuvet method for creatinine.

DISCUSSION

With the simultaneous measurement of creatinine and albumin in urine, the albumin/creatinine ratio can be determined effectively reducing or eliminating the occasional false-negative and false-positive result in those with dilute or concentrated urines, respectively. The dipstick test for these analytes permits the simple identification of individuals with possible albuminuria and could serve well in a point-of-care setting.

A new liquid homogeneous assay for HDL cholesterol determination evaluated in seven laboratories in Europe and the United States

We evaluated a new liquid homogeneous assay for the direct measurement of high density lipoprotein cholesterol (HDL-C Plus) in seven laboratories. The assay includes two reagents which can be readily used in most available clinical chemistry analyzers. The total CVs of the new method were below 4.6% and the bias in relation to the designated comparison method was below 3.9%. The total error ranged between 4 to 7%. HDL-C values determined by this method were in good agreement with those obtained by the old homogeneous assay using lyophilized reagents, and other homogeneous and precipitation assays (0.944 < r < 0.996). The assay was linear up to at least 3.89 mmol/l HDL-C. Hemoglobin did not interfere, whereas in icteric samples slight deviations were observed. Lipemia up to 11.3 to 22.6 mmol/l triglycerides did not interfere with this homogeneous HDL-C assay. In samples of patients with paraproteinemia, discrepant results were seen. This liquid homogeneous HDL-C assay was easy to handle and produced similar results in all laboratories participating in this study. This method will enable clinical laboratories to reliably measure HDL-C for risk assessment of coronary heart disease.

Measurement of phosphatidylserine exposure in leukocytes and platelets by whole-blood flow cytometry with annexin V

Phosphatidylserine (PS) exposure serves as a procoagulant stimulus and a signal for phagocytic clearance of apoptotic cells. In order to measure PS exposure in blood cells, we developed a flow-cytometric procedure to measure annexin V binding to leukocytes and platelets in whole-blood samples. Leukocytes were identified by CD45 and side-scatter gating, and platelets by CD6 1 and side-scatter gating. The absolute number of annexin V molecules bound per cell was determined from an independent calibration procedure. Normal populations had the following levels of annexin V binding (in molecules per cell): lymphocytes, 0.53 x 10(3) neutrophils, 1.75 x 10(3) monocytes, 2.45 x 10(3) platelets, 0.14 x 10(3). These levels represent </= 0.1% of the values obtained after maximal stimulation of PS exposure with calcium ionophore, confirming that virtually all PS is intracellular in normal circulating leukocytes and platelets. Pretreatment of whole-blood samples with ammonium chloride to lyse erythrocytes caused a 9- to 300-fold increase in annexin V binding to leukocytes, indicating that analysis of unlysed whole-blood samples is essential to avoid artifactual increases in annexin V binding to leukocytes. Comparison of annexin V with two other markers of platelet activation, CD62P and the activation-dependent epitope of glycoprotein IIb/IIIa detected by the PAC I antibody, indicated that platelets from normal donors showed the least amount of activation with the annexin V marker. Whole-blood flow cytometry with annexin V can reliably measure the state of PS exposure in platelets and leukocytes, and the results confirm that these cell

Homogeneous HDL-cholesterol assay versus ultracentrifugation/dextran sulfate-Mg2+ precipitation and dextran sulfate-Mg2+ precipitation in healthy population and in hemodialysis patients

OBJECTIVES

To evaluate the analytical performance of a new homogeneous HDL-cholesterol assay (Olympus Diagnostica). To investigate possibly discrepant results in chronic hemodialysis patients who commonly exhibit quantitative and qualitative lipoprotein abnormalities, responsible for atherogenic complications in these patients.

DESIGN AND METHODS

Serum samples were collected from 50 healthy subjects and 65 chronic hemodialysis patients. HDL-C levels measured by the homogeneous assay were compared with the routine dextran sulfate-Mg2+ precipitation method and the ultracentrifugation/dextran sulfate-Mg2+ precipitation as reference method.

RESULTS

The homogeneous assay was linear up to at least 220 mg/dL. The analytical precision was estimated with three different sets of commercial controls and one set of human pooled serum control. The within-day CV ranged between 1.7% and 3.8% and the between-day CV ranged between 1.0% and 2.3%. HDL-C values in both populations correlated highly with the dextran sulfate-Mg2+ precipitation method and the ultracentrifugation/dextran sulfate-Mg2+ precipitation method (r > or = 0.96, bias between -0.9 and 2.3 mg/dL). Lipemia up to triglyceride concentration of 600 mg/dL did not alter the HDL-C value.

CONCLUSIONS

The homogeneous assay for HDL-C (Olympus) uses much less sample, is accurate and convenient to handle, and allows full automation. The test should considerably facilitate the screening of individuals at an increased risk of cardiovascular disease, including hemodialysis patients.

Biochemical risk factors and patient's outcome: the case of lipoprotein(a)

Lipoprotein(a) (Lp(a)) is a genetic variant of low density lipoproteins and consists of the covalent association of the unique and enigmatic apolipoprotein(a) to apoliprotein B100. Despite the high degree of homology with low density lipoproteins, Lp(a) displays distinctive physico-chemical properties, function and metabolism. The present article reviews the main biological and clinical evidences about the association between raised concentration of Lp(a) and atherothrombotic diseases and provides tentative guidelines to improve the clinical usefulness of Lp(a) measurements.

A new system for rapid measurement of ATP

The paper introduces a new type instrument for rapid measuring ATP. The system consists of a micromodule ATP sensor and an instrument for measuring weak light transmitted by optic fiber. The micromodule ATP sensor mainly is composed of enzyme membrane, a probe and a bundle of optic fiber. The instrument measuring weak light consists of photomultiplier, high voltage power, pulse amplifier and counter. The instrument was characterized by simple structure, small size, rapid response time (< 5s), high sensitivity (10(-12) mol/L), stable performance (measuring the same sample for 50 times, CV < 5%), long enzyme storage time (> 3 months).

Comparison of 2 homogeneous high-density lipoprotein cholesterol assays

BACKGROUND

High-density lipoprotein cholesterol (HDL-C) is an independent inverse risk factor for coronary artery disease. Current methodologies for measurement of HDL-C in most clinical laboratories involve chemical precipitation-based methods. However, these methods are time-consuming, affected by high triglycerides, are not suitable for complete automation, and require a large sample size. New direct homogeneous methods are now available that do not have these constraints.

DESIGN

We evaluated the performance of 2 direct homogeneous methods, Liquid N-geneous HDL-C assay (LN-HDL) and Boehringer Mannheim HDL Cholesterol assay (BM-HDL), and compared these methods against a modified Centers for Disease Control and Prevention reference method (MR-HDL) in 126 patients with normotriglyceridemia (triglycerides < 4.5 mmol/L, range 0.6-4.3 mmol/ L) and 50 patients with hypertriglyceridemia (triglycerides > or =4.5 mmol/L, range 4.5-18.8 mmol/L).

RESULTS

Excellent precision profiles were exhibited by both homogeneous methods. Both LN-HDL and BM-HDL correlated well with MR-HDL in normotriglyceridemia (r = 0.98, slope = 0.93 and r = 0.97, slope = 1.0, respectively). However, compared with the modified reference method, the LN-HDL correlated better than the BM-HDL in hypertriglyceridemic samples (r = 0.97, slope = 1.0 and r = 0.91, slope = 0.9, respectively). The 1998 National Cholesterol Education Program guidelines for accuracy (bias < +/-5%) were met by LN-HDL in both normotriglyceridemic and hypertriglyceridemic samples (bias = 1.3% and 3.3%, respectively); however, BM-HDL failed to meet the National Cholesterol Education Program accuracy criteria in both triglyceride subgroups (bias = 8.2% and 11.3%, respectively). In addition, the total error for LN-HDL in both normotriglyceridemia (6.6%) and hypertriglyceridemia (8.6%) was well within the National Cholesterol Education Program guidelines for total error (< or =13%); BM-HDL exhibited a higher total error than LN-HDL in normotriglyceridemia (11.9%) and failed to meet the National Cholesterol Education Program guidelines in hypertriglyceridemia (15.0%).

CONCLUSION

Although both homogeneous methods are precise, the LN-HDL assay is superior in accuracy to the BM-HDL assay when compared with the modified reference method.

Reported alcohol consumption and the serum carbohydrate-deficient transferrin test in third-year medical students

The serum carbohydrate-deficient transferrin (CDT) test was performed on 143 third-year medical students along with questionnaires for the self-reporting of alcohol consumption during the last 2 weeks, the last 6 months, and questions on any alcohol-related untoward events. We found that the CDT test has poor sensitivity for detecting binge drinking in our population of students, despite some likely under-reporting of drinking. Self-reporting of drinking is commonly unreliable, and we found no significant correlation between the CDT concentrations in serum and the magnitude of self-reported alcohol use during 2-week and 6-month periods. Hangover was by far the commonest self-reported untoward event, and there was a highly significant relationship (P < 0.001) between drinking and untoward events. From a small population of non-drinkers, we estimated the reference ranges for CDT to be <27 U/l for men and <35 U/l for women.

Fourier transform infrared and Raman microspectroscopy of materials in tissue

Fourier transform infrared and Raman (FT-IR and FT-Raman) microspectroscopy were used to study materials found in human tissue. Individual cases involving cholesterol, calcium stearate, and a polystyrenesulfonate ion exchange resin demonstrate the utility of the spectroscopic data. Characteristic spectral bands for these materials were compared with those of authentic chemical species to confirm their identities. The role of vibrational spectroscopy in pathologic diagnoses is discussed.