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Biomedical subjects

A O Okorodudu

Publications and source records attributed to A O Okorodudu.

At least 19 recordsLinked to original sources
PubMed2005

Analytical evaluation of HgbA1c, microalbumin, CRP, and RF on Architect ci8200 integrated system and workflow performance evaluation using computer simulation.

BACKGROUND: Recently, hemoglobin A1c (HgbA1c), microalbumin (MA), C-reactive protein (CRP) and rheumatoid factor (RF) have been introduced on high throughput general chemistry system. We evaluated analytical performance of these assays on an integrated clinical chemistry and immunoassay analyzer and studied the impact of testing these assays on these systems on the overall efficiency of the analyzer, via computer simulation. METHODS: The analytical performance was measured by determining precision, linearity and correlation of patient sample results with in-house testing methodology. MedModel simulation software is used to develop simulation model and process efficiency is determined by measuring turnaround times and resource utilization. RESULTS: Between-days CVs ranged from 8.59% for MA to 3.22% for HgbA1c level 1 controls. Less than 2% carryover for all 4 methods was observed on the integrated analyzer. For HgbA1c on HPLC analyzer, the minimum and maximum TAT for a batch of 50 samples was 3.78 and 160 min, respectively, while for the integrated system it was 28.2 and 35.1 min, respectively. Labor utilization for the 2 processes ranged from 3.21% to 3.75%. CONCLUSION: Chemistry module on an integrated system can be used to determine the HgbA1c and other serum proteins.

Albuminuria↗
PubMed2004

Sex hormone regulation of systemic endothelial and renal microvascular reactivity in type-2 diabetes: studies in gonadectomized and sham-operated Zucker diabetic rats.

BACKGROUND: Male Zucker diabetic rats exhibit a more severe endotheliopathy in comparison with their female diabetic litter mates. The plasma concentrations of both thromboxanes and endothelins are elevated in diabetes, and the receptor cross-talk between TXA(2) and ET-1 receptors may be enhanced in type-2 diabetic Zucker rats. AIMS: To determine the role of the endogenous sex steroid hormones, testosterone and estradiol on the systemic and renal microvascular reactivity to ET-1, thromboxane-mimetic U46619, ET-TXA(2) receptor interaction, and the nitric oxide vasodilator system in Zucker hypertensive-diabetic rats. METHODS: Male and female Zucker rats aged 8-10 weeks were each divided into two groups. The male rats were castrated or underwent a sham operation. The female rats were spayed (bilateral ovariectomy and hysterectomy) or had a sham operation. All rats were studied 4-6 weeks after the gonadectomy or sham operations. Blood glucose and insulin as well as plasma concentrations of testosterone and estradiol were determined. Haemodynamic studies were undertaken with determination of the dose-response curve for mean arterial pressure (MAP), renal cortical flow (RCF) and renal medullary blood flow (MBF) in response to ET-1 and U46619, and the effect of interdiction of the ET-TXA(2) interaction with ET-antagonists BQ610 and BQ788. The role of endogenous NO was assessed by its response to graded acetylcholine doses and to a L-NG-nitro-arginine methyl ester (L-NAME) infusion. RESULTS: Castrated male rats had a significantly lower blood glucose concentration (295 +/- 33 mg dL(-1)) compared with their sham-controls (481 +/- 40 mg dL(-1)), P = 0.008. Mean arterial pressure tended to be lower in the castrated rats. Gonadectomy reduced the plasma testosterone and estradiol concentrations. Castration abolished the hypotensive action of U46619 compared with sham-operated male rats (P < 0.0001, anova). Conversely, the pressor action of U46619 seen in the sham-operated female rats was reversed to a profound hypotensive action in the spayed rats (P < 0.001, anova). The change in MAP after U46619 was inversely correlated to the plasma testosterone concentration (r = -0.73, P = 0.027). The paradoxical hypotensive response elicited by ET-1 in the Zucker diabetic rats of both sexes was abolished by castration only (P < 0.005, anova). Castration caused a significant (P = 0.011) augmentation of the vasodilator response to acetylcholine, while spaying caused a slight attenuation. Castration, but not spaying, resulted in significant increases in MBF after U46619 (P = 0.003, anova), ET-1 (P = 0.005, anova) and acetylcholine (P = 0.053, anova). The ET-(B) antagonist BQ788 augmented the U46619-induced rise in MAP in castrated male rats, and also abolished the U46619-induced increase in MBF (P < 0.01 anova). L-NAME (25 mg kg(-1)) increased MAP and decreased MBF in the gonadectomized and sham-operated rats, except for the castrated male Zucker rats, where it significantly increased MBF (+90 +/- 31 PU) (P = 0.0004, anova) despite the increase in MAP. CONCLUSIONS: Testosterone and estradiol regulate systemic and microvascular reactivity to TXA(2) receptor stimulation in type-2 diabetic Zucker rats. The impact of testosterone on blood glucose concentration, blood pressure, and the systemic and renal microcirculatory response to ET-1 and NO, as well as the endothelin-thromboxane receptor cross talk, is greater, and opposite to that of estradiol. The effects of testosterone withdrawal may at least in part be mediated by the ET-B receptor subtype and NO generation. Androgen blockade should be investigated further for the reversal or delay of hypertensive-diabetic endotheliopathy.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2001

Ionized magnesium in the homeostasis of cells: intracellular threshold for Mg(2+) in human platelets.

The role of extracellular magnesium ions in the homeostasis of intracellular ionized magnesium ([Mg(2+)](i)) in human platelets was studied. For media containing 0.00 to 0.60 mmol/l of extracellular ionized magnesium ([Mg(2+)](o)), the mean [Mg(2+)](i) fluctuated between 533 and 760 micromol/l. As the [Mg(2+)](o) was increased to 1.5 mmol/l, the [Mg(2+)](i) increased proportionately and peaked at 1470.1 micromol/l. Additional increase in the [Mg(2+)](o) from 1.50 to 6.00 mmol/l resulted in decreased [Mg(2+)](i) until it equilibrated between 739 and 776 micromol/l. The influx of Mg(2+) at [Mg(2+)](o) of 0.60 and 1.50 mmol/l was studied using verapamil, a calcium channel inhibitor, and ouabain, an inhibitor of the Na/K pump, respectively. The verapamil (25 mmol/l) blocking experiments resulted in a 92.4% inhibition of the Mg(2+) influx into the platelet at a [Mg(2+)](o) of 1.50 mmol/l. Ouabain (0.5 and 2.5 mmol/l) showed an enhancement effect on the influx of Mg(2+) at [Mg(2+)](o) of 0.60 mmol/l and no effect at 1.50 mmol/l. The effect of verapamil indicates that ion channels that are homologous to calcium ion channels may be involved in the influx of Mg(2+) into the platelets. The inhibition of Mg(2+) influx for [Mg(2+)](o) greater than 1.50 mmol/l may illustrate a protective mechanism that attempts to maintain the viability of platelets at abnormally high [Mg(2+)](o). These results suggest that there is an intracellular Mg(2+) threshold of 1500 micromol/l, above which an active mechanism prevents further influx of Mg(2+).

Blood Platelets↗
PubMed2001

Accuracy and precision of point-of-care testing for glucose and prothrombin time at the critical care units.

The use of point-of-care testing (POCT) in critical care patient units has continued to increase since the 1980s. This increase is due to the need for prompt therapeutic interventions that may impact mortality and morbidity, and reduce the overall cost of healthcare for critically ill patients. The diagnostic manufacturing industry has risen to this challenge by introducing portable and/or handheld analyzers for use at the point-of-care. In order to ensure the public safety in the USA, the Food and Drug Administration (FDA) must approve the use of each POCT analyzer. The FDA approval is based on established performance criteria that includes relative accuracy and precision documentation. This study evaluated the precision and accuracy of the POCT prothrombin time and glucose analyzers relative to the manufacturers' specifications, to the internal QC in the main laboratory, and to the results of the external proficiency-testing program. The QC for the prothrombin time had a precision that ranged from 2.84% to 3.45% (POCT) and from 1.27-1.66% (main laboratory). The precision for the glucose QC ranged from 5% to 5.2% (POCT) and 0.9-2.7% (main laboratory). Using the results of the external proficiency testing, the inter-laboratory CV% for the POCT prothrombin time ranged from 3.5% to 5.0% and the main laboratory had a range of 2.5-2.9%. The inter-laboratory CV% ranges for glucose POCT and the main laboratory were 4.9-10.6% and 1.8-3.5%, respectively. The main laboratory analyzers proved to be more accurate than the POCT analyzers as indicated by comparison to the mean prothrombin time and glucose results of all participating laboratories in the proficiency testing program.

Blood Glucose↗
PubMed2000

Apparatus and method for interfacing capillary electrophoresis and chemiluminescence nitrogen detection for the analysis of nitrogen-containing compounds.

We have developed an interface that allows the specific detection of nitrogen-containing compounds by using a chemiluminescence nitrogen detector. The feasibility of using this interface was demonstrated by separating and detecting two nitrogen-containing compounds, p-aminosalicylic acid and L-phenylalanine. Although baseline separation was achieved, the theoretical plates were lower when compared to UV detection (25000 vs. approximately 85000). A sensitivity of 75 ng (approximately 500 pmol) per injection was achieved with this system which is adequate for pharmaceutical and biotech applications.

Aminosalicylic Acid↗
PubMed2000

Stability of prothrombin time and activated partial thromboplastin time tests under different storage conditions.

Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are common laboratory tests that are useful in the diagnosis of coagulation disorders and monitoring anticoagulant therapy. Recent expansions in the outreach laboratory services at our institution prompted us to investigate the shipping limitations for some tests, including PT and aPTT. Although we followed NCCLS guidelines for the collection of blood specimens, we observed falsely elevated PT and aPTT values due to the different storage conditions. The objective of this study is to determine the effect of conditions and duration of storage on PT and aPTT tests using plasma and whole blood samples, respectively. For this study, 36 plasma samples with normal and prolonged PT and aPTT were exposed to different storage conditions. Blood was centrifuged immediately and plasma was stored at room temperature (RT), refrigerated at 4 degrees C, or frozen at -20 degrees C. The samples were analyzed at 0 h and repeated at 6, 12 and 24 h under various conditions. Although statistically significant differences were observed for plasma samples for normal PT tests after 12 h at refrigerated and frozen storage conditions, the differences would not change the clinical interpretation of the results. On the other hand, samples stored refrigerated or at RT showed significant differences for aPTT at 24 h. These differences would change clinical interpretation, especially for samples with normal or near normal aPTT times. Interestingly, aPTT was significantly higher for samples stored frozen when compared to refrigerated and RT conditions at 6 h. Similar patterns were also observed on ten whole blood samples with normal PT and aPTT values. In conclusion, either plasma or whole blood samples can be accepted for PT testing up to 24 h and for aPTT testing up to 12 h only, when transported either at RT or at 4 degrees C.

Humans↗
PubMed2000

Prospective study of IgM to Toxoplasma gondii on Beckman Coulter's Access(TM) immunoassay system and comparison with Zeus ELISA and gull IFA assays.

We compared a new assay for Toxoplasma IgM on the Access analyzer (Beckman Coulter, Inc., Chaska, MN, USA), a random access instrument based on the principle of paramagnetic particle enzyme immunoassay with an enzyme-linked immunosorbent assay (ELISA) (Zeus Scientific, Inc., Raritan, NJ, USA) and an immunofluorescent assay (IFA) (Gull Laboratories, Inc., Salt Lake City, UT, USA). Four hundred fresh, unfrozen clinical samples from pregnant women (n = 154), HIV positive patients (n = 41), and patients in whom infection with Toxoplasma gondii was suspected (n = 200) were collected and assayed over a three month period. The specificity of the Access assay was compared to the consensus results. Results that were discrepant between the ELISA and IFA were resolved using a third IFA (Zeus). Once resolved, the specificity for the Access assay, the Zeus ELISA and the Gull IFA were 99.22%, 97.91%, and 99.45%, respectively. We conclude that the Access assay specificity is comparable to consensus results, minimizing false positive results; and because it is a random access instrument, it may be preferable over batch methods.

Adolescent↗
PubMed2000

Multiple site analytical evaluation of a portable blood gas/electrolyte analyzer for point of care testing.

OBJECTIVE: To evaluate the analytical performance of the SenDx 100 portable blood gas and electrolyte analyzer (SenDx Medical, Carlsbad, CA). DESIGN: Accuracy was evaluated by correlation of whole blood patient samples with the Nova Stat Profile 5 (Nova Biomedical, Waltham, MA) and the Ciba Corning 865 (Chiron Diagnostics, Medford, MA). Precision was evaluated using quality control materials (RNA Medical, Acton, MA). SETTING: Critical care laboratories and operating rooms in two institutions. MEASUREMENTS AND MAIN RESULTS: Precision studies performed at three different concentration levels for each analyte demonstrated intra-assay precision of < or =2.5% coefficient of variation and interassay precision of < or =4.0% coefficient of variation in all cases. Analysis of patient specimens in general showed good to excellent correlation to reference analyzers. Regression variables are tabulated. CONCLUSIONS: The SenDx 100 portable blood gas and electrolyte analyzer is a simple and easy to use analyzer demonstrating acceptable performance compared with reference methods.

Blood Gas Analysis↗
PubMed1999

Development of a urinary free cortisol assay using solid-phase extraction-capillary electrophoresis.

In clinical practice, the measurement of urinary free cortisol (UFC) provides the most sensitive and specific diagnostic information for excess adrenal production of cortisol. The existing methodologies (RIA and HPLC) are time consuming, costly, involve tedious extractions, derivatizations and problems with non-specific interactions with cortisol metabolites in urine. In the present study, we describe the development of an SPE-CE method for the rapid analysis of UFC. UFC was concentrated using SPE C18 cartridges (3M Empore) under a vacuum and eluted with acetonitrile-SDS. The use of 10% acetone to wash cartridges before final elution with acetonitrile-SDS showed significant improvements in the free cortisol recovery. The complete extraction was accomplished in 10-15 min with a recovery of 89-94%. CE analysis was done on a Beckman P/ACE 5010 with detection at 254 nm using a neutral capillary. Detection limits of free cortisol in urine was improved to 10 microg/l with SPE compared to 500 microg/l without SPE. No interferences either from BSA or other urinary cortisol metabolites affected the free cortisol determinations. The results showed the feasibility of a rapid UFC detection with improved sample handling capacity.

Electrophoresis, Capillary↗
PubMed1998

Multicenter study of oxygen-insensitive handheld glucose point-of-care testing in critical care/hospital/ambulatory patients in the United States and Canada.

OBJECTIVES: Existing handheld glucose meters are glucose oxidase (GO)-based. Oxygen side reactions can introduce oxygen dependency, increase potential error, and limit clinical use. Our primary objectives were to: a) introduce a new glucose dehydrogenase (GD)-based electrochemical biosensor for point-of-care testing; b) determine the oxygen-sensitivity of GO- and GD-based electrochemical biosensor test strips; and c) evaluate the clinical performance of the new GD-based glucose meter system in critical care/hospital/ambulatory patients. DESIGN: Multicenter study sites compared glucose levels determined with GD-based biosensors to glucose levels determined in whole blood with a perchloric acid deproteinization hexokinase reference method. One site also studied GO-based biosensors and venous plasma glucose measured with a chemistry analyzer. Biosensor test strips were used with a handheld glucose monitoring system. Bench and clinical oxygen sensitivity, hematocrit effect, and precision were evaluated. SETTING: The study was performed at eight U.S. medical centers and one Canadian medical center. PATIENTS: There were 1,248 patients. RESULTS: The GO-based biosensor was oxygen-sensitive. The new GD-based biosensor was oxygen-insensitive. GD-based biosensor performance was acceptable: 2,104 (96.1%) of 2,189 glucose meter measurements were within +/-15 mg/dL (+/-0.83 mmol/L) for glucose levels of < or = 100 mg/dL (< or = 5.55 mmol/L) or within +/-15% for glucose levels of > 100 mg/dL, compared with the whole-blood reference method results. With the GD-based biosensor, the percentages of glucose measurements that were not within the error tolerance were comparable for different specimen types and clinical groups. Bracket predictive values were acceptable for glucose levels used in therapeutic management. CONCLUSIONS: The performance of GD-based, oxygen-insensitive, handheld glucose testing was technically suitable for arterial specimens in critical care patients, cord blood and heelstick specimens in neonates, and capillary and venous specimens in other patients. Multicenter findings benchmark the performance of bedside glucose testing devices. With the new +/-15 mg/dL --> 100 mg/dL --> +/-15% accuracy criterion, point-of-care systems for handheld glucose testing should score 95% (or better), as compared with the recommended reference method. Physiologic changes, preanalytical factors, confounding variables, and treatment goals must be taken into consideration when interpreting glucose results, especially in critically ill patients, for whom arterial blood glucose measurements will reflect systemic glucose levels.

Adult↗
PubMed1998

Serum interleukin-6 in bacterial and nonbacterial acute otitis media.

BACKGROUND: Increasing prevalence of antibiotic-resistant bacteria is a serious clinical problem that calls for reduction of unnecessary use of antibiotics. Acute otitis media (AOM) is the most common reason for antibiotic therapy in the United States. Approximately 30% of AOM cases do not have a bacterial etiology. Rapid identification of these cases could help withhold unnecessary antibiotic treatment. OBJECTIVE: To determine the usefulness of serum levels of interleukin-6 (IL-6), an acute phase cytokine shown to be a reliable marker of neonatal bacterial infection, in differentiation between bacterial and nonbacterial AOM in children. STUDY DESIGN: IL-6 was measured in stored serum samples from 184 children (mean age, 22 months) with AOM who were enrolled in antibiotic efficacy trials at our department. The samples were obtained at enrollment and at 9 to 12 days after initiation of antibiotic therapy. Sera from 21 uninfected children (mean age, 23 months) were used as controls. The etiology of AOM was determined by bacterial and viral cultures as well as respiratory syncytial virus antigen detection in the middle ear fluids obtained by tympanocentesis. RESULTS: Bacterial etiology of AOM was confirmed in 125 children (68%), whereas in 59 children (32%) no bacterial pathogen could be detected in the middle ear fluid. Children with bacterial AOM had significantly higher IL-6 levels than those with nonbacterial AOM (median, 11.5 vs 3.7 pg/mL). However, this difference was almost entirely attributable to pneumococcal AOM specifically. IL-6 levels in children with AOM caused by Streptococcus pneumoniae were significantly higher (median, 40.1 pg/mL) than in AOM caused by Haemophilus influenzae (7.3 pg/mL) or Moraxella catarrhalis (6.8 pg/mL). At the cutoff value of 30 pg/mL, the specificity of IL-6 for detection of pneumococcal AOM was 91% with a sensitivity of 61%, but its sensitivity for detection of bacterial AOM in general was only 27%. CONCLUSIONS: Low levels of IL-6 do not rule out bacterial etiology of AOM in general; therefore, IL-6 is not sensitive enough as a marker of bacterial AOM. Surprisingly, serum IL-6 levels in pneumococcal AOM were significantly higher than the levels associated with other bacterial AOM, and serum IL-6 levels of >30 pg/mL were highly specific for pneumococcal AOM. These findings suggest a distinctive role for S pneumoniae in the pathogenesis of AOM.

Acute Disease↗
PubMed1994

Intracellular ionized calcium and increasing doses of lithium chloride therapy in healthy Sprague-Dawley rats.

The use of lithium salts in the prophylaxis and treatment of several psychiatric and neurologic disorders continues to be well accepted despite the apparent lack of understanding regarding its mode of action at the molecular level. This lack of delineation in the mechanism of action is supported by numerous conflicting publications. Despite the lack of understanding, a role for calcium in the manifestation of lithium's action is a constant singular consensus. Intracellular ionized calcium ([Ca2++]i) is involved in the proper functioning of cells because of its role in the second messenger pathway. It is therefore essential to evaluate the effect of lithium on intracellular calcium metabolism in a well-defined system. In this study, platelets loaded with Fura-2-Acetoxymethyl were used to evaluate the effect of intraperitoneally administered lithium chloride at 0, 2.5, 5.0, 7.5, and 10 mmol/kg body wt. on [Ca++]i. The results showed a slight relative increase in serum Ca++ that correlated well with the dose of LiCl administered to the rats. The baseline [Ca++]i were comparable in the study groups, but the response to thrombin stimulation was more pronounced at LiCl doses of 2.5, 5.0, and 7.5/kg body wt. compared with control and rats treated with 10 mmol LiCl/kg body wt. This finding suggests a dose-dependent response of [Ca++]i to LiCl treatment. The observation may therefore explain the variations that have been reported in [Ca++]i studies with respect to LiCl therapy using different doses.

Animals↗
PubMed1992

Frozen human serum reference material for standardization of sodium and potassium measurements in serum or plasma by ion-selective electrode analyzers.

Three interlaboratory round-robin studies (RR1, RR2, and RR3) were conducted to identify a serum-based reference material that would aid in the standardization of direct ion-selective electrode (ISE) measurements of sodium and potassium. Ultrafiltered frozen serum reference materials requiring no reconstitution reduced between-laboratory variability (the largest source of imprecision) more than did other reference materials. ISE values for RR3 were normalized by the use of two points at the extremes of the clinical range for sodium (i.e., 120 and 160 mmol/L), with values assigned by the flame atomic emission spectrometry (FAES) Reference Method. This FAES normalization of ISE raw values remarkably improved all sources of variability and unified the results from seven different direct ISE analyzers to the FAES Reference Method value. Subsequently, a three-tiered, fresh-frozen human serum reference material was produced to the specifications developed in RR1-RR3, was assigned certified values for sodium and potassium by Definitive Methods at the National Institute of Standards and Technology (NIST), and was made available in 1990 to the clinical laboratory community as a Standard Reference Material (SRM); it is now identified as SRM 956. Albeit retrospectively, we show how applying an FAES normalization step identical to that used in RR4/5 to the ISE data for SRM 956 after the NIST Definitive Method values were known, consistently moved the ISE results for RR3 closer to the true value for Na+ and K+.

Electrodes↗
PubMed1991

Accuracy of common drug screen tests.

Forty consecutive urine specimens, obtained from patients seen in the emergency center, positive for either cocaine and/or marijuana, were analyzed using five methods of analysis. A new latex agglutination inhibition assay, Abuscreen OnTrak, (Roche Diagnostic Systems, Nutley, NJ), was compared with four other drug abuse assays: mass spectrometry, (Hewlett-Packard Co, Richardson, TX); an automated homogeneous enzyme immunoassay technique, ETS System, (Syva Co, Palo Alto, CA); a manual enzyme multiplied immunoassay technique; EMIT-st, (Syva); and a fluorescence polarization immunoassay, TDx, (Abbott Laboratories, Chicago, IL). For statistical purposes, mass spectrometry was the reference point for the presence or absence of a specific substance. All instrument sensitivities, with the exception of mass spectrometry, were set with the same "cut off" point of 100 micrograms/L for marijuana and 300 micrograms/L for cocaine and its metabolites. Efficiency in the detection of cocaine and its metabolites was 95% by all methods. Efficiency for the detection of marijuana and its metabolites ranged from 70% (Roche's OnTrak) to 90% (Syva's ETS). Simple to use, assays of minimal cost are presently available for rapid, accurate drug of abuse screening.

Evaluation Studies as Topic↗
PubMed1990

Evaluation of three first-generation ion-selective electrode analyzers for lithium: systematic errors, frequency of random interferences, and recommendations based on comparison with flame atomic emission spectrometry.

Ion-selective electrode analyzers for measuring lithium (Li/ISE) in serum became available in early 1987. We compared results for patients' samples from three of them vs results from flame atomic emission spectrometry (FAES). Within-run and day-to-day imprecision ranged from 0.01 to 0.03 mmol/L and 0.01 to 0.04 mmol/L, respectively. Comparing Li/ISE results (y) with the FAES results (x) gave the following equations: y = 1.063x - 0.035 for AMDEV's Lytening 2, y = 1.020x + 0.038 for NOVA's Model 11, and y = 1.030x - 0.027 for AVL's Model 985. Unexplained positive errors greater than 0.2 mmol/L were observed for two of the 90 patients' samples, but only a few additional excessively high values were seen in 3000 patients' samples run subsequently (Lytening 2). Causes of error in clinical Li/ISE measurements are still unclear; simply characterizing them as "matrix effects" does not correct the underlying analytical problem. An increase in pH from loss of CO2 gave low results on two of the three Li/ISE analyzers but did not change FAES results. Trimethylammonium bicarbonate used in a reconstitution solution caused extremely high Li/ISE results but did not change FAES results. Performance specifications to help reduce and correct these errors are recommended.

Chemistry, Clinical↗