New creatinine sensor for point-of-care testing of creatinine meets the National Kidney Disease Education Program guidelines

Addition of the measurement of creatinine concentration in whole blood on the ABL837 FLEX blood gas analyzer (Radiometer Medical ApS, Copenhagen, Denmark) allows fast and reliable reporting of creatinine in point-of-care testing (POCT). The new creatinine sensor follows the international recommendations of the National Kidney Disease Education Program Laboratory Working Group as of January 2006 with respect to acceptable performance, reference method and traceability. Validation tests show that the creatinine sensor has excellent performance and thus has the potential to change the poor track record of creatinine testing in plasma and whole blood in both the clinical laboratory and POCT. This article describes the clinical needs and the methods currently available for creatinine measurement and presents performance tests carried out by the manufacturer.

Clinical laboratory values during diabetic pregnancies

BACKGROUND

Physiological pregnancy can affect routine laboratory tests, e.g., the erythrocyte sedimentation rate increases above the reference range for healthy non-pregnant adults and little is known about whether diabetes and pregnancy together can cause additional changes that require monitoring of blood-tests.

OBJECTIVE

The purpose of this study was to investigate changes in clinical chemistry and haematological laboratory test results during pregnancies of type 1 diabetics and to compare the results with changes during normal pregnancies.

METHODS

We studied 25 type 1 diabetic women with standard clinical chemistry and haematological blood-tests during pregnancy.

RESULTS

Haemoglobin, haematocrit, and erythrocyte number decreased until the 3rd trimester and leucocytes and platelets did not change significantly. The erythrocyte sedimentation rate increased by over 200%. Protein and albumin decreased until the 3rd trimester to below the reference range. Urea did not change, creatinine decreased and uric acid increased within the reference range. AST and ALT remained within the reference range. Alkaline phosphatase and leucine aminopeptidase increased until above the reference range. Cholesterol and triglycerides increased until the third trimester above results from normal pregnancies.

CONCLUSION

A wide range of biochemistry and haematology laboratory values changed during diabetic pregnancy comparable to physiological pregnancies. No additional routine laboratory-testing during diabetic pregnancies compared with physiological pregnancies is required.

Ionized calcium: whole blood, plasma or serum?

OBJECTIVES

To determine an optimal specimen type to be used for measurements of ionized calcium (iCa) so that it applies properly to the reference interval. Also to determine the validity of the pH correction that is applied to iCa measurements.

METHODS

A reference interval study of normal volunteers was performed using four sample types namely balanced heparin (BH) whole blood, lithium heparin (LH) whole blood, plasma and serum. The sample was treated in an anaerobic fashion and analyzed at 0 and 40 minutes after venipuncture. The effect of pH correction as well as analysis time after collection was also studied.

RESULTS

The mean iCa was the highest in BH-treated whole blood when measured immediately. However, it was slightly lower at 40 min after collection (p < 0.001). In contrast, there did not appear to be a significant difference in results when LH-treated whole blood was analyzed at 0 or 40 min. The reference interval for serum was similar to that of whole blood. The reference interval for plasma was dramatically lower than whole blood and plasma. The reference intervals for pH adjusted ionized calcium (iCa-adj) were dramatically lower than those from all specimens without adjustment. The reason for this was that the reference interval for pH in this study had a strong alkaline bias on one instrument and a strong acidic bias on the other.

CONCLUSIONS

The sample of choice for ionized calcium analysis appears to be whole blood with either BH or LH. For the LH specimen, there is no significant change over 40 min whereas there is significant change for the BH specimens (-0.030 mmol/L, p < 0.0001). iCa-adj should not be used unless (i) very strict attention is paid to standardization of both the calcium and the pH and (ii) there is a very good reason to believe that the patients' pH is normal at 7.4.

Gold nanoparticles for the development of clinical diagnosis methods

The impact of advances in nanotechnology is particularly relevant in biodiagnostics, where nanoparticle-based assays have been developed for specific detection of bioanalytes of clinical interest. Gold nanoparticles show easily tuned physical properties, including unique optical properties, robustness, and high surface areas, making them ideal candidates for developing biomarker platforms. Modulation of these physicochemical properties can be easily achieved by adequate synthetic strategies and give gold nanoparticles advantages over conventional detection methods currently used in clinical diagnostics. The surface of gold nanoparticles can be tailored by ligand functionalization to selectively bind biomarkers. Thiol-linking of DNA and chemical functionalization of gold nanoparticles for specific protein/antibody binding are the most common approaches. Simple and inexpensive methods based on these bio-nanoprobes were initially applied for detection of specific DNA sequences and are presently being expanded to clinical diagnosis. Figure Colorimetric DNA/RNA detection using salt induced aggregation of AuNP-DNA nanoprobes.

Comparison of automated assays for the determination of vitamin B12 in serum

OBJECTIVES

To study the agreement of serum cobalamin results obtained with three different widely used analyzers.

DESIGN AND METHODS

Comparative measurement of 100 serum samples was performed using the Abbott Architect, the Bayer Centaur, and the Roche Elecsys 2010 analyzer.

RESULTS

Relatively close numeric correlation of the results was found with Pearson's r>0.95 for all three comparisons; however, the mean concentration of the highest reading and the lowest reading method differed by 16%.

CONCLUSIONS

Relatively good agreement of results from three automated serum cobalamin assays was observed.

Evidence-based laboratory medicine - a guide for critical evaluation of in vitro laboratory testing

Evidence-based laboratory medicine (EBLM) is an essential part of modern laboratory medicine practice. This review presents a guide for better understanding and implementing the EBLM process. The process of EBLM begins with development of a clinically relevant question. Tools for assisting in question formulation include the Patient Intervention Comparator and Outcome (PICO) or Case Assay Predicate and Outcome (CAPO) strategies. Locating evidence that addresses the question is performed using resources available on the internet. Systematic reviews that have objectively collated evidence addressing the question can be particularly useful. The evidence collected must be critically appraised using checklists developed for this purpose. Diagnostic performance of tests is frequently stated in terms of sensitivity, specificity, negative and positive predictive values, and the diagnostic odds ratio. Evaluating 95% confidence limits is important for interpretation. Likelihood ratios for tests in disease states are also important for converting pre-test probabilities to post-test probabilities using Bayes Theorem. Tools such as Receiver Operator Characteristic curves and Fagan's diagram are important analytical and visual aids. Laboratorians must give thoughtful consideration into conveying information to clinicians in a useful format. Evidence-based guidelines and collaboration with clinicians are important for development of local care paths. Auditing the effectiveness of implemented care paths is an important part of quality management. In conclusion, effective use of EBLM can benefit patients by helping laboratorians provide the best-available information in the clinically relevant time frame. Presenting the information appropriately maximizes clinical application of the best evidence.

Analytic evaluation of the beta-human chorionic gonadotropin assay on the Abbott IMx and Elecsys2010 for its use in doping control

OBJECTIVES

The principal objective of this study was to compare the analytical performance of the Elecsys2010 (Roche Diagnostics) system with the IMx (Abbott laboratories) system for beta-hCG assay in order to assess its possible utility as a confirmation test for the quantitative measurement of beta-hCG in urine for doping control purposes.

DESIGN AND METHODS

Urine samples with spiked standard known concentrations of beta-hCG and different urine samples from athletes were used in order to determine the calibration curve stability and linearity, detection limit, total, within-run and between-run precision, and method comparison for the IMx and Elecsys2010 systems for beta-hCG assay, along with the stability of samples, at room temperature and at 4 degrees C.

RESULTS

The IMx assay was linear up to 500 IU/L, whereas the Elecsys2010 assay was linear up to 1000 IU/L. The detection limit for the IMx and Elecsys2010 systems were 0.75 IU/L and 0.25 IU/L, respectively. The total precision of the IMx and Elecsys2010 systems were <or=5% for beta-hCG concentrations ranging from 20 to 900 IU/L and from 6.67 to 55.2 IU/L, respectively. The within-run precision tests for the IMx and Elecsys2010 systems yielded CV results of 2-3% and 3-4% respectively, while the between-run precision for the Elecsys2010 was less than 4%, whereas that of IMx was 9-16%. Regression analysis with spiked urine samples yielded the following: slope (SD) 0.7104 (0.003) and y-intercept (SD) -0.4286 (1.397) (Sy.x=2.328; r=0.9999; n=5), whereas regression analysis using the athletes' urine samples yielded the following results: slope (SD) 0.3692 (0.003) and y-intercept (SD) 0.0016 (0.003) (Sy.x=0.0096; r=0.9924; n=100). Sample stability studies evidenced a nonsignificant effect at 4 degrees C and room temperature (25 degrees C) for up to 1 month.

CONCLUSIONS

For doping control, the IMx and Elecys2010 may be used to screen and confirm the presence of beta-hCG in urine of athletes, respectively. Additional studies are needed to verify this finding. This study also underscores the need for beta-hCG assays standardization for doping control.

A Unified Approach for Assessing Agreement for Continuous and Categorical Data

This paper proposes several Concordance Correlation Coefficient (CCC) indices to measure the agreement among k raters, with each rater having multiple (m) readings from each of the n subjects for continuous and categorical data. In addition, for normal data, this paper also proposes the coverage probability (CP) and total deviation index (TDI). Those indices are used to measure intra, inter and total agreement among all raters. Intra-rater indices are used to measure the agreement among the multiple readings from the same rater. Inter-rater indices are used to measure the agreement among different raters based on the average of multiple readings. Total-rater indices are used to measure the agreement among different raters based on individual readings. In addition to the agreement, the paper also assess intra, inter, and total precision and accuracy. Through a two-way mixed model, all CCC, precision and accuracy, TDI, and CP indices are expressed as functions of variance components, and GEE method is used to obtain the estimates and perform inferences for all the functions of variance components. Each of previous proposed approaches for assessing agreement becomes one of the special case of the proposed approach. For continuous data, when m approaches infinity, the proposed estimates reduce to the agreement indices proposed by Barnhart et al. (2005). When m = 1, the proposed estimate reduces to the ICC proposed by Carrasco and Jover (2003). When m = 1, the proposed estimate also reduces to the OCCC proposed by Lin (1989), King and Chinchilli (2001a) and Barnhart et al. (2002). When m = 1 and k = 2, the proposed estimate reduces to the original CCC proposed by Lin (1989). For categorical data, when k = 2 and m = 1, the proposed estimate and its associated inference reduce to the kappa for binary data and weighted kappa with squared weight for ordinal data.

Column-switching LC-MS/MS analysis for quantitative determination of testosterone in human serum

BACKGROUND

An accurate measurement of testosterone is needed in many clinical applications for correct diagnosis and appropriate treatment. Our aim was to develop a fast and robust high-throughput LC-MSMS method for quantification of serum testosterone in women.

METHODS

Testosterone was derivatized by oximation and extracted with methyl tert-butyl ether from 200 microL of serum. Further matrix elimination was achieved on-line using a column-switching LC-method. The instrumental analysis was performed on an API4000 tandem mass spectrometer equipped with an Agilent series 1312A binary pump and an Agilent series 1311A quaternary pump. The MRM transitions were 304-->124 and 304-->112 for testosterone and 307-->124 and 307-->112 for d(3)-testosterone.

RESULTS

The total analysis time of the column-switching method was 3 min. Linear calibration curves were obtained in the concentration range from 0.035 nmol/L (0.01 microg/L) to 6.92 nmol/L (2 microg/L). Within-day and between-day precision, expressed as the relative standard deviation at four different concentrations ranged from 4.70% to 9.35%. Correlation with the in-house method (solvent-extraction RIA) showed r(2)=0.920.

CONCLUSIONS

The presented column-switching method offers a simple, fast and economical analysis of testosterone in human serum. The procedure requires only small sample volumes and is well suited for quantification of testosterone in serum from women and children.

Assessing routine and serum markers of liver fibrosis in CHB patients using parallel and serial interpretation

OBJECTIVE

The purpose of this study was to determine the cut-offs of serum biomarkers of liver fibrosis in HBsAg-positive patients by receiver operating characteristic (ROC) curves, and to determine the validity of these markers in parallel and serial interpretation.

METHODS

This study included 444 HBsAg-positive patients who had liver biopsy performed between January 1, 2003 and March 31, 2006. Some routine and clinical chemistry tests were run, and the stage of liver fibrosis was measured. The cut-offs of those markers were identified by using ROC curves. Sensitivity, specificity, predictive values (both positive and negative), and the Youden's index of these markers were calculated in parallel and serial interpretation.

RESULTS

The 444 patients were divided into a training group (322 patients) and a validation group (122 patients). All markers except gender, HB and TP were found to be statistically significant factors associated with significant fibrosis in the training group. The AUROC of GGT, APRI, AGE-PLT and AST in the training group were 0.772, 0.769, 0.748 and 0.700, respectively, and their sensitivities in the validation group were 65.00%, 70.00%, 75.00% and 60.00%, respectively. In parallel interpretation, the highest sensitivity was 85.00% at AGE-PLT union or logical sum AST, and in serial interpretation, the best specificity was 96.34% at GGT intersection AGE-PLT.

CONCLUSION

A few routine and serum biomarkers can be used to effectively assess most patients with HBsAg-positive CHB with and without significant liver fibrosis in parallel and serial interpretation.

A kinetic method amenable to automation for ceruloplasmin estimation with inexpensive and stable reagents

OBJECTIVES

To develop a kinetic, inexpensive, automatable assay for ceruloplasmin as ferroxidase.

DESIGN AND METHODS

Dithiothreitol has been used to stabilize the substrate and quinolones to complex the ferric.

RESULTS

Mean ferroxidase activity in healthy adults, Wilson's disease and pregnancy was 787.29, 178.5 and 1828.09 IU/L, respectively. Correlation coefficient of ferroxidase vis-à-vis copper, ferroxidase by ferrozine and ceruloplasmin were 0.90, 0.94 and 0.92, respectively.

CONCLUSIONS

Norfloxacin method is a simple, inexpensive and automatable kinetic assay.

Complete blood count, clinical chemistry, and serology profile by using a single tube of whole blood from mice

Clinical pathology is a valuable means for assessing specific organ pathology and a screening tool for general animal health. Routine clinical pathology evaluation in mice usually includes whole blood for a complete blood count (CBC) and a clinical biochemistry analysis. Acquisition and analysis of these samples can be problematic due to the small volumes of blood that can be obtained from a mouse. Typically, a complete blood count requires blood from a tube containing an anticoagulant, whereas a clinical biochemistry profile needs blood from a serum clot tube. Because of the small volume that can be obtained, splitting the blood from a single mouse into 2 different tubes may result in inadequate samples to perform the desired tests or introduce inaccuracies. We explored the feasibility of using a single lithium heparin tube for generation of a CBC, biochemistry profile, and serology profile. We also evaluated the consistency of CBC data, including the quality of a peripheral blood smear taken from a lithium heparin or EDTA tube after various storage times. We found that CBC, biochemistry, and serology profiles could be obtained more readily when blood samples were placed in a single lithium heparin tube than in 2 separate tubes. In addition, the quality of blood smears and CBC results from the lithium heparin tube were comparable (with few exceptions) to those from an EDTA tube after prolonged storage.

Renal function--estimation of glomerular filtration rate

Assessment and follow-up of renal dysfunction is important in the early detection and management of chronic kidney disease. The glomerular filtration rate (GFR) is the most accurate measurement of kidney disease and is reduced before the onset of clinical symptoms. Drawbacks to the measurement of GFR include the high cost and incompatibility with routine laboratory monitoring. Serum creatinine determination is a mainstay in the routine laboratory profile of renal function. The measurement of serum cystatin C has been proposed as a more sensitive marker for GFR. According to National Kidney Foundation-K/DOQ1 clinical guidelines for chronic kidney disease, serum markers should not be used alone to assess GFR. Based on prediction equations, clinical laboratories should report an estimate of GFR, in addition to reporting the serum value. In this article, information is presented on how best to estimate GFR using prediction equations for adults and for children. Using serum creatinine concentration with the Modification of Diet in Renal Disease (MDRD) study equation offers a suitable estimation of GFR in adults. The cystatin C prediction equation with the use of a prepubertal factor seems superior to creatinine-based prediction equations in children of <14 years.

Automation and validation of a fast method for the assessment of in vivo oxidative stress levels

BACKGROUND

The d-ROMs test for the evaluation of serum hydroperoxides (HP) is simple, reliable, and cheap. Furthermore, it can easily be adapted to automated analyzers. Changing from the manual to an automated procedure allows the simultaneous processing of a large number of samples in a greatly reduced time, avoiding manual handling of samples and reagents and reducing variability sources.

METHODS

This study was performed to adjust the manual procedure to a routine automated method in the clinical laboratory. We carried out the d-ROMs test in sera from 90 subjects of both sexes (34 men and 56 women) with age ranging from 20 to 80 years (mean 51+/-14 years). All subjects were free from acute or chronic inflammatory disease, immunological disease and history or evidence of malignancy. Subjects were not on vitamin and/or antioxidant therapies.

RESULTS

The detection limit of the assay was 40 AU. Linearity was observed up to 475 AU. The recovery ranged between 97% and 105%. Within- and between-run imprecision was <5%. The mean HP value was 304+/-8 AU, with no significant difference between men (291+/-10 AU) and women (311+/-11 AU). A significant positive correlation was observed between age and HP in the whole population (r=0.4, p=0.0002).

CONCLUSIONS

The automated test for the estimation of serum hydroperoxides represents a reliable and feasible procedure for increasing efficiency and reducing costs compared to the manual method, and is particularly suitable for evaluating oxidative stress in a variety of clinical conditions.

Effect of Plasma Volume Loss during Graded Exercise Testing on Blood Lactate Concentration

Previous studies have shown that plasma volume (PV) loss can be a confounding variable in the interpretation of changes in blood constituents. We examined the effect of PV loss on three features of the blood lactate versus work-rate relationship, namely, slight blood lactate increase during the early stages of graded exercise testing (GXT); work rate at the onset of a systematic increase in blood lactate, i.e., lactate threshold (LT); and work rate at a blood lactate concentration of 4 mM, i.e., onset of blood lactate accumulation (OBLA). Fourteen subjects underwent cycle ergometer GXT. Blood samples were obtained at rest and at the end of each 3-min work-rate increment and analyzed for hematocrit and lactate concentration. For exercise levels up to and including LT, PV loss was relatively stable at approximately 2.8%. Beyond LT, PV loss accelerated. From the first work rate to LT, blood lactate concentration uncorrected for PV loss increased 0.24 +/- 0.07 mM (P < 0.05). After correction for PV loss, the increase was 0.21 +/- 0.08 mM (P < 0.05). These mean increases were not significantly different from each other. For the four exercise levels above LT common to most subjects, PV-corrected lactate values were significantly lower than uncorrected values. Correction of lactate values for PV loss did not alter LT for any subject, but it did result in a significant increase in OBLA. Thus, PV loss has the potential to be a confounding variable for the interpretation of blood lactate parameters that are determined at exercise levels above LT.

Roche Elecsys Prolactin II assay: reactivity with macroprolactin compared with eight commercial assays for prolactin and determination of monomeric prolactin by precipitation with polyethylene glycol

Hyperprolactinaemia due to macroprolactin (MPRL) can lead to misdiagnosis and inappropriate treatment. We studied the new Roche Elecsys Prolactin assay (PRL II) which has been developed to reduce reactivity with MPRL. We investigated the performance of the PRL II assay at six laboratory sites to determine precision and establish reference intervals for total immunoreactive PRL and for monomeric PRL determined by precipitation with polyethylene glycol (PEG). We compared the reactivities with macroprolactin of the PRL II, the PRL I and seven other PRL assays. The PRL II assay reacted less strongly than the PRL I assay and similarly to the ADVIA Centaur assay with macroprolactin. PEG precipitation can be used with the PRL II assay to estimate the concentration of monomeric PRL.

Sample preparation in lab-on-a-chip systems

Fully integrated lab-on-chip systems are relatively rare, and no current system can claim to be able to perform all the roles of a laboratory. This article outlines ways of combining specific single modules to form a fully integrated lab-on-a-chip system for deoxyribonucleic acid analysis.

Roche Elecsys Prolactin II assay: reactivity with macroprolactin compared with eight commercial assays for prolactin and determination of monomeric prolactin by precipitation with polyethylene glycol

Hyperprolactinaemia due to macroprolactin (MPRL) can lead to misdiagnosis and inappropriate treatment. We studied the new Roche Elecsys Prolactin assay (PRL II) which has been developed to reduce reactivity with MPRL. We investigated the performance of the PRL II assay at six laboratory sites to determine precision and establish reference intervals for total immunoreactive PRL and for monomeric PRL determined by precipitation with polyethylene glycol (PEG). We compared the reactivities with macroprolactin of the PRL II, the PRL I and seven other PRL assays. The PRL II assay reacted less strongly than the PRL I assay and similarly to the ADVIA Centaur assay with macroprolactin. PEG precipitation can be used with the PRL II assay to estimate the concentration of monomeric PRL.

Cholesterol Profile Measurement by Vertical Auto Profile Method

Vertical auto profile (VAP) method is a direct single test for measuring comprehensive lipoprotein cholesterol profile. It is based on a well-established method of ultracentrifugation that uses vertical rotor and single density gradient spin. VAP provides cholesterol concentrations of total lipoprotein, high-density lipoprotein (HDL), low-density lipoprotein (LDL), very-low-density lipoprotein (VLDL), lipoprotein(a) (Lp(a)), intermediate-density lipoprotein (IDL), HDL subclasses (HDL2 and HDL3), LDL subclasses (LDL1, LDL2, LDL3, and LDL4), VLDL subclasses (VLDL1, VLDL2, and VLDL3), and LDL maximum time, which is directly proportional to LDL size. Because VAP measures additional lipoprotein classes, such as Lp(a), IDL, and subclasses of HDL, LDL, and VLDL, it can identify patients at high risk for coronary heart disease who cannot be identified using the standard lipid panel. In addition, the VAP method is compliant with the National Cholesterol Education Program's Adult Treatment Panel III guidelines.

Reflective testing--what do our service users think?

BACKGROUND

Reflective testing incorporates the clinical judgement, knowledge and experience of an individual biochemist to request additional tests appropriate to the clinical scenario. Despite being vigorously debated within the biochemistry profession, little is known about how the clinicians directly involved in patient care feel about it. We have conducted a survey to elicit our service users' opinion of reflective testing.

METHODS

Ten clinical scenarios, each involving the possible addition of a specific test, were circulated to 520 hospital doctors and 152 general practitioners. The four response options were to add further tests, phone and discuss the case, add a comment to the original results or do nothing.

RESULTS

A total of 216 (32%) responses were received. Overall, the majority were in favour of 'adding on' free triiodothyronine (86%), gamma-glutamyltransferase (78%), lipid profile (59%), thyroid peroxidase antibodies (63%), pituitary hormones (58%), troponin (55%) and serum electrophoresis (68%) in the given scenarios. However, only 30% would like a pregnancy test added and only 45% a prostate-specific antigen added without prior consultation. The response differed according to grade and specialty.

CONCLUSIONS

Reflective testing is generally welcomed by our service users, provided the nature and implications of the specific test is considered in addition to the full clinical scenario.

Reflective testing: what do patients think?

INTRODUCTION

Reflective testing refers to the practice of adding on tests by laboratory staff. Little is known about what patients think of this practice.

METHODS

We surveyed patients attending a general practice surgery and patients attending hospital outpatient clinics. We sought their views about the practice of adding on tests and about the information they received from requesting clinicians about their investigations.

RESULTS

In both groups of patients, large majorities favoured an approach in which relevant additional tests are performed without consulting the requesting clinician or patient first. Most patients also felt that the requesting clinicians had provided a satisfactory explanation about what tests were to be performed and why.

CONCLUSION

Most patients are content to let NHS professionals add on relevant tests if this is felt to be in their interest.

Antibody Arrays: Technical Considerations and Clinical Applications in Cancer

Antibody arrays represent one of the high-throughput techniques that are able to detect multiple proteins simultaneously. One of the main advantages of this technology over other proteomic approaches is that the identities of the measured proteins are known or can be readily characterized, allowing a biological interpretation of the results. Features such as lower sample volume and antibody concentration requirements, higher format versatility, and reproducibility support the increasing use of antibody arrays in cancer research. Clinical applications include disease marker discovery for diagnosis, prognosis, and drug response, characterization of signaling and protein pathways, and modifications associated with disease development and progression. This report presents an overview of technical issues of the main antibody array formats and various applications in cancer research. Antibody arrays are high-throughput tools that improve the functional characterization of molecular bases for disease. Furthermore, identification and validation of protein expression patterns, characteristic of cancer progression, and tumor subtypes may intervene and improve tailored therapies in the clinical management of cancer patients.