CYP2D6 inhibition by diphenhydramine leading to fatal hydrocodone overdose

OBJECTIVES

Fatal drug overdoses often involve multiple co-intoxicants, including opioids. Hydrocodone, the most prescribed opioid for pain management, is metabolized to the active metabolite hydromorphone by hepatic CYP2D6. Inhibition of CYP2D6 by other compounds can disrupt the analgesic properties of hydrocodone and extend its half-life. Diphenhydramine is an over-the-counter cold medication and is known to inhibit CYP2D6 activity.

CASE PRESENTATION

A woman in her late 50s was prescribed hydrocodone/acetaminophen (Norco® 10/325). Days before her death, she began taking diphenhydramine for cold symptoms. A post-mortem toxicology report detected the following compounds by High Performance Liquid Chromatography/Time of Flight-Mass Spectrometry (LC/TOF-MS) analysis: acetaminophen (14 μg/mL), hydrocodone (410 ng/mL), dihydrocodeine (24 ng/mL), and diphenhydramine (150 ng/mL). Hydromorphone was not detected (<2 ng/mL). All compounds were detected in therapeutic concentrations, except for hydrocodone, which was present at lethal concentrations.

CONCLUSIONS

This case highlights a fatal drug-drug interaction between hydrocodone and diphenhydramine. The estimated total body burden of hydrocodone was 6- to 12-fold higher than acetaminophen, which is unexpected, as these two drugs were administered as a single formulation and have similar half-lives. Furthermore, hydromorphone was undetectable. Taken together, these findings are highly suggestive of a fatal opioid overdose precipitated by diphenhydramine.

Endogenous and iatrogenic sources of variability in response to opioid therapy in Post-Surgical and injured orthopedic patients

BACKGROUND

Hydrocodone is the most prescribed opioid in the US. The objective was to evaluate associations between genetic, intrinsic, and extrinsic patient factors, plasma hydrocodone and metabolites, common side effects, and pain scores in a cohort of orthopedic surgery patients.

METHODS

Data for each patient was collected by review of the electronic hospital record (EHR), and patient interview. Patients were recruited from those with trauma or undergoing scheduled elective surgery for total knee replacement or total hip at the University of Louisville Hospital, Baptist East Hospital, and Jewish Hospital, Louisville, KY. Plasma opiate concentrations and a targeted genotyping panel was performed.

RESULTS

There were statistically significant correlations with daily (p < 0.001) and total dose (p = 0.002) of hydrocodone in hospital and duration of opioid therapy. The length of opioid administration was significantly shorter in CYP2D6 EM/UM versus CYP2D6 PM/IM patients (p = 0.018). Subjects with the OPRM1 c.118G variant were also on opioids longer (p = 0.022). The effect of co-administration of a CYP2D6 inhibitor had a significant effect on the length of opioid therapy (P < 0.001). And not surprisingly the effect of the inhibitor adjusted CYP2D6 phenotype was greater in both the hospital stay period and days of opioid use post hospital discharge (p < 0.001).

CONCLUSIONS

Based on this study, patients should be evaluated for the use of inhibitors of CYP2D6, during hydrocodone therapy can alter the phenotype of the patient (phenocopy) and increase the probability that the patient will be on opioids for longer periods of time.

A Shared Diagnostic Stewardship Approach toward Improving Autoimmune Encephalopathy Send-out Testing Utilization

BACKGROUND

For many laboratories, autoimmune encephalopathy (AE) panels are send-out tests. These tests are expensive, and ordering patterns vary greatly. There is also a lack of consensus on which panel to order and poor understanding of the clinical utility of these panels. These challenges were presented to our newly formed, multidisciplinary, diagnostic stewardship committee (DSC). Through this collaboration, we developed an algorithm for ordering AE panels; combining diagnostic criteria with practice guidelines.

METHODS

We analyzed test-ordering patterns in 2018 and calculated a true-positive rate based on clinical presentation and panel interpretation. An evidence-based approach was combined with input from the Department of Neurology to synthesize our algorithm. Efficacy of the algorithm (number of panels ordered, cost, and true positives) was assessed before and after implementation.

RESULTS

In 2018, 77 AE-related panels were ordered, costing $137 510. The true-positive rate was 10%, although ordering multiple, similar panels for the same patient was common. Before implementing the algorithm (January 1-July 31, 2019), 55 panels were ordered, costing $105 120. The total true-positive rate was 3.6%. After implementation, 23 tests were ordered in a 5-month period, totaling $50 220. The true-positive rate was 13%.

CONCLUSION

With the DSC-directed mandate, we developed an algorithm for ordering AE panels. Comparison of pre- and postimplementation data showed a higher true-positive rate, indicating that our algorithm was able to successfully identify the at-risk population for AE disorders. This was met with a 43% decrease in the number of tests ordered, with total cost savings of $25 000 over 5 months.

ELISA-based detection of Open Reading Frame protein 1 in patients at risk of developing lung cancer

BACKGROUND

Early detection of lung cancer significantly improves survival outcomes. Thus, lung cancer screening for high-risk individuals using low-dose CT scan (LDCT) is recommended. LDCT has several limitations, and often requires invasive follow up. Previously, we have developed an ELISA for measurement of Open Reading Frame 1 protein (ORF1p) in serum. We assessed whether ORF1p can be used as a risk assessment biomarker for patients at high risk for developing lung cancer.

PATIENTS

Patients with risk factors for lung cancer were enrolled in our study with consent under IRB approval. A total of 122 patients were included. The lung cancer cohort consisted of 38 patients with varying stages of cancer undergoing treatment.

METHODS

ORF1p quantification was performed using our ELISA assay on serum samples.

RESULTS

ORF1p was significantly increased in the serum of patients with identified lung nodules compared to those without nodules (P = 0.0007). ORF1p was also significantly increased in patients who were recommended for follow up (P = 0.0004). When comparing the at-risk cohort to patients with lung cancer, there was not a significant difference in ORF1p levels.

CONCLUSION

ORF1p can be used to identify patients at high risk of developing lung cancer and may provide an effective, non-invasive risk assessment marker to complement LDCT screening.

Verification of Newly FDA-Approved Kappa and Lambda Free Light Chain Assays on a Previously Untested Platform

BACKGROUND

κ and λ free light chains (FLCs) are monitored to aid in the diagnosis of plasma cell disorders. Our goal was to validate the Diazyme Human κ and λ assays on Beckman Coulter UniCel DxC 800 Synchron and compare to Freelite κ and λ assays on Roche Cobas Integra.

METHODS

Linearity verification, within- and between-run precision, method comparison, and reference range (RR) verification were conducted using CLSI guidelines. Statistical analysis was performed using EP Evaluator^®. Mean, SD, CV, and bias were determined.

RESULTS

Diazyme κ FLC assay was linear within 0.00-191.00 mg/L. Diazyme λ FLC assay was linear within 0.00-205.30 mg/L. Diazyme κ FLC QC1 had a mean of 16.70 mg/L, CV of 7.0%. QC2 had a mean of 33.37 mg/L, CV of 2.6%. Diazyme λ FLC QC1 had a mean of 21.73 mg/L, CV of 2.3%. QC2 had a mean of 42.05 mg/L, CV of 1.5%. Bias of DxC-Diazyme FLCs compared to Integra-Freelite FLCs was -2.55 mg/L (κ FLC), and 4.54 mg/L (λ FLC). Qualitative comparison of κ FLC assays indicated 100% agreement for both normal and abnormal values. For λ FLC assay, agreement was 95% for normal values and 75% for abnormal values. For κ/λ ratio there was 50% agreement for normal values, and 100% for abnormal values. For RR verification, 1 sample was outside the Diazyme κ RR. For λ, all samples were within the manufacturer's RR.

CONCLUSIONS

Diazyme assays for FLCs have excellent precision and accuracy and are comparable to Freelite assays.

Lack of Influence by CYP3A4 and CYP3A5 Genotypes on Pain Relief by Hydrocodone in Postoperative Cesarean Section Pain Management

Background

Genetic polymorphisms of cytochrome P450 are contributors to variability in individual response to drugs. Within the P450 family, CYP2D6 is responsible for metabolizing hydrocodone, a widely prescribed opioid for pain management. Alternatively, CYP3A4 and CYP3A5 can form norhydrocodone and dihydrocodeine. We have previously found that in a postcesarean section cohort, the rate of hydromorphone formation was dependent on the genotype of CYP2D6 and that plasma hydromorphone, not hydrocodone, was predictive of pain relief.

Method

Blood was obtained from a postcesarean cohort that were surveyed for pain response and common side effects. Plasma samples were genotyped for CYP3A4/5, and their hydrocodone concentrations were measured by LC-MS. R statistical software was used to check for differences in the outcomes due to CYP3A4/5 and CYP2D6, and a multivariate regression model was fit to determine factors associated with pain score.

Results

Two-way ANOVA between CYP3A4/A5 and CYP2D6 phenotypes revealed that the former variants did not have a statistical significance on the outcomes, and only CYP2D6 phenotypes had a significant effect on total dosage (P = 0.041). Furthermore, a 3-way ANOVA analysis showed that CYP2D6 (P = 0.036) had a predictive effect on plasma hydromorphone concentrations, and CYP3A4/A5 did not have any effect on the measured outcomes.

Conclusions

With respect to total dosages in a cesarean section population, these results confirm that CYP2D6 phenotypes are predictors for plasma hydromorphone concentration and pain relief, but CYP3A4/A5 phenotypes have no influence on pain relief or on side effects.

Does an antibiotic nail made in a lubricated tube release antibiotic?

INTRODUCTION

The treatment of long-bone osteomyelitis has long been a difficult problem. Recently, antibiotic-impregnated intramedullary rods for the treatment of infected long-bone fractures have been gaining popularity but they are quite difficult to fabricate. Recently, a new technique that utilizes mineral oil to coat the inside of a chest tube mold prior to introduction of cement has been proven to ease fabrication. We hypothesized that the use of mineral oil would alter the elution characteristics of tobramycin from the intramedullary device.

METHODS

Two groups of antibiotic nails were fabricated under sterile conditions. The control group utilized a chest tube mold. The study group utilized a chest tube that was coated with mineral oil prior to cement injection. Each intramedullary nail was placed in pooled human serum and incubated under physiologic conditions. The level of tobramycin in each sample was measured at timepoints 0, 1, 6, and 24 h.

RESULTS

There was no significant difference when comparing control with the experimental group at any timepoint. Antibiotic nails eluted tobramycin at a rapid rate in the first 6 h of exposure to serum, regardless of their preparation with oil or without oil. The rate of elution fell precipitously between 6 and 24 h.

CONCLUSION

We believe that although this study, as with any study, cannot perfectly recreate in vivo conditions, we have clearly shown that mineral oil has no significant effect on elution of tobramycin from antibiotic nails.

Multicenter evaluation of analytical characteristics of the Elecsys® Periostin immunoassay

OBJECTIVE

The multifunctional cytokine IL-13 is thought to play a central role in Type 2 inflammation in asthma. Serum periostin has been explored as a candidate biomarker for evaluating IL-13 activity in the airway. We describe the technical performance characteristics of a novel, fully automated immunoassay for the determination of periostin in serum.

DESIGN AND METHODS

Limit of blank [LoB], limit of detection [LoD] and limit of quantitation [LoQ], linearity, precision and reproducibility across sites and lots were evaluated according to Clinical and Laboratory Standards Institute guidelines. Interferences and sample stability were also investigated.

RESULTS

The pre-specified values for LoB (2ng/mL), LoD (4ng/mL) and LoQ (10ng/mL) were met. The assay was linear throughout the measuring range (10-160ng/mL) with recoveries within ±10% of target at concentrations >30ng/mL and within ±3ng/mL at concentrations ≤30ng/mL. Recovered periostin concentrations were also within ±10% of target in presence of 43 potentially interfering substances and drugs. Samples were stable across various storage conditions and durations (24h at room temperature, 7days at 4°C, 12weeks at -20°C, and 3 freeze/thaw cycles). Repeatability experiments resulted in CVs across samples and controls ranging from 0.9-1.5%. Intermediate precision was 1.2-1.7% and reproducibility including 3 testing sites and 3 reagent lots was 1.7-3.1%. The final assay correlates to the assay version used in previous clinical trials (Pearson's r=0.998, bias at 50ng/mL=1.2%).

CONCLUSION

The performance evaluation of the Elecsys^® Periostin immunoassay including a multicenter precision analysis demonstrated that the assay is suitable for measuring serum periostin at clinically important concentrations around 50ng/mL.

Demographic data for urinary Acute Kidney Injury (AKI) marker [IGFBP7]·[TIMP2] reference range determinations

This data in brief describes characteristics of chronic stable comorbid patients who were included in reference range studies of [IGFBP7]·[TIMP-2] “Reference Intervals of Urinary Acute Kidney Injury (AKI) Markers [IGFBP7]·[TIMP2] in Apparently Healthy Subjects and Chronic Comorbid Subjects without AKI” [1]. In order to determine the specificity of [IGFBP7]·[TIMP-2] for identifying patients at risk of developing AKI we studied a cohort with nine broad classification of disease who did not have AKI. Details regarding the population that was targeted for inclusion in the study are also described. Finally, we present data on the inclusion criteria for the healthy subjects used in this investigation to determine the reference range.

A clinical approach to solving discrepancies in therapeutic drug monitoring results for patients on sirolimus or tacrolimus: Towards personalized medicine, immunosuppression and pharmacogenomics

BACKGROUND

Unexpected clinical laboratory concentrations often need to be investigated before they are acted upon in a clinical setting. Therapeutic drug monitoring (TDM) frequently involves drugs with narrow therapeutic windows and can be harmful to the patient if changes are made based on erroneous serum drug concentrations. Too little of the drug will result in ineffective therapy and too much of the drug can cause life threatening toxicities. There are many factors that can result in unexpected serum drug concentrations including differences in analytical methods being used, diet, timing of blood draw, genotype and compliance. All these factors should all be considered before deciding if changes should be made in a patient's therapeutic course.

CASE REPORT

We determined the cause of 2 patient's unexpected TDM concentrations for sirolimus and tacrolimus. Using this approach in 2 patient cases, we describe how co-treatment and uncommon genotypes result in unexpected drug concentrations.

CONCLUSIONS

Both cases involved unexpected drug values. In the first case, the cause was revealed to be a drug that was added to the patient's treatment regimen (posaconazole) that inhibits CYP3A4 which is responsible for sirolimus metabolism. In the second case, the patient was revealed to have an uncommon genotype for CYP3A5, causing higher metabolism and lower serum tacrolimus concentrations than the general population.

Undetected hypoglycemia in a patient receiving TPN

CASE REPORT

A 58-year-old female was admitted to the hospital in a severely malnourished state. She was treated for Crohn's disease with total parental nutrition (TPN). The patient's blood glucose was monitored by point of care (POC) testing every 4h, and a specimen is also drawn daily for metabolic assessment. The POC blood glucose values were consistently much higher than the lab values. Humalog insulin (5 U) was given to the patient to decrease high blood glucose levels that developed following administration of TPN. The patient then became hypoglycemic as a result of this insulin treatment. POC glucose testing, performed every 4h, did not detect the iatrogenic hypoglycemia, while lab glucose results were not given close attention. The lab sample was always drawn 1-2h after insulin was given to the patient and resulted in a lower blood glucose value. In addition, the symptoms of hypoglycemia such as shaking and dizziness were masked by the patient's poor health status, supine position, and the continuously given TPN.

CONCLUSIONS

These findings highlighted the importance of the correct sampling time following insulin administration and the consideration of the lab results in addition to POC. The patient's insulin regimen was modified to prevent further hypoglycemic events.

The role of hydromorphone and OPRM1 in postoperative pain relief with hydrocodone

BACKGROUND

Postoperative pain management remains a challenge for clinicians due to unpredictable patient responses to opioid therapy. Some of this variability may result from single nucleotide polymorphisms (SNPs) of the human opioid mu-1 receptor (OPRM1) that modify receptor binding or signal transduction. The OPRM1 variant with the highest frequency is the A118G SNP. However, previous studies have produced inconsistent results regarding the clinical effects of A118G on opioid response. We hypothesized that measurement of serum opioid concentrations, in addition to determining total opioid consumption, may provide a more precise method of assessing the effects of A118G on analgesic response. The current study evaluated the relationship of analgesia, side effects, total hydrocodone consumption, quantitative serum hydrocodone and hydromorphone concentrations, and A118G SNP in postoperative patients following Cesarean section.

METHODS

158 women scheduled for Cesarean section were enrolled prospectively in the study. The patients had bupivacaine spinal anesthesia for surgery and received intrathcal morphine with the spinal anesthetic or parenteral morphine for the first 24 hours after surgery. Thereafter, patients received hydrocodone/acetaminophen for postoperative pain control. On postoperative day 3, venous blood samples were obtained for OPRM1 A118G genotyping and serum opioid concentrations.

RESULTS

131 (82.9%) of the subjects were homozygous for the 118A allele of OPRM1 (AA) and 27 (17.1%) carried the G allele (AG/GG). By regression analysis, pain relief was significantly associated with total hydrocodone dose in the AA group (P = 0.01), but not in the AG/GG group (P = 0.554). In contrast, there was no association between pain relief and serum hydrocodone concentration in either group. However, pain relief was significantly associated with serum hydromorphone concentration (a metabolite of hydrocodone) in the AA group (P = 0.004), but not in the AG/GG group (P = 0.724). Conversely, side effects were significantly higher (P < 0.04) in the AG/GG group (mean = 6.4) than in the AA group (mean = 4.4), regardless of adjustment for BMI, pain level, or total dose of hydrocodone.

CONCLUSION

This study found a correlation between pain relief and total hydrocodone dose in patients homozygous for the 118A allele (AA) of the OPRM1 gene, but not in patients with the 118G allele (AG/GG). However, pain relief in 118A patients did not correlate with serum hydrocodone concentrations, but rather with serum hydromorphone levels, the active metabolite of hydrocodone. This suggests that pain relief with hydrocodone may be due primarily to hydromorphone. Although pain relief did not correlate with opioid dose in AG/GG patients, they had a higher incidence of opioid side effects. The correlations identified in this study may reflect the fact that serum opioid concentrations were measured directly, avoiding the inherent imprecision associated with relying solely on total opioid consumption as a determinant of opioid effectiveness. Thus, measurement of serum opioid concentrations is recommended when assessing the role of OPRM1 variants in pain relief. This study supports pharmacogenetic analysis of OPRM1 in conjunction with serum opioid concentrations when evaluating patient responses to opioid therapy.

An overview of a recent court challenge to the protection of biomarkers as intellectual property

BACKGROUND

We present an intellectual property case in the United States to demonstrate the recent developments concerning patenting novel biomarker discoveries. A court struck down several patents owned by Myriad Genetics, which were related to breast cancer (BRCA1 and BRCA2). This decision can affect patent eligibility for inventions related to biomarkers, particularly genetic biomarkers.

METHODS

The court proceedings for the Myriad Genetics case were reviewed by two patent attorneys (SCH and JMT). Relevant discussions applicable to the scientist involved with biomarker discovery were also prepared.

RESULTS

In this case, the Plaintiff had argued that the analysis and comparison of various gene mutations merely involved natural phenomena, and, therefore, could not be eligible for patent protection. The patent holder (Myriad) argued that the claimed gene compositions did not exist in nature, and that the claimed methods provided practical utility for science and medicine. The Court held that the patent claims did not meet patent eligibility requirements under United States patent law. It held that the patent claims at issue were merely abstract mental processes of analyzing and comparing gene sequences, and that such abstract mental processes are not patentable. On June 22, 2010, Myriad appealed the ruling.

CONCLUSIONS

This case provides guidance to inventors in the biomarker field who may be interested in obtaining intellectual property protection for their inventive work, as well as their patent counsel. However, the case also presented unique factors that may not be present in all situations involving biomarker patents.

The journey to regulation of protein-based multiplex quantitative assays

BACKGROUND

Clinical proteomics presents great promise in biology and medicine because of its potential for improving our understanding of diseases at the molecular level and for detecting disease-related biomarkers for diagnosis, prognosis, and prediction of therapeutic responses. To realize its full potential to improve clinical outcome for patients, proteomic studies have to be well designed, from biosample cohorts to data and statistical analyses. One key component in the biomarker development pipeline is the understanding of the regulatory science that evaluates diagnostic assay performance through rigorous analytical and clinical review criteria.

CONTENT

The National Cancer Institute's Clinical Proteomic Technologies for Cancer (CPTC) initiative has proposed an intermediate preclinical "verification" step to close the gap between protein-based biomarker discovery and clinical qualification. In collaboration with the US Food and Drug Administration (FDA), the CPTC network investigators recently published 2 mock submission review documents, first-of-their-kind educational materials that may help the scientific community interested in developing products for the clinic in understanding the likely analytical evaluation requirements for multiplex protein technology-based diagnostic tests.

CONCLUSIONS

Building on this momentum, the CPTC continues with this report its collaboration with the FDA, as well as its interactions with the AACC and the Centers for Medicare and Medicaid Services, to further the understanding of regulatory requirements for approving multiplex proteomic platform-based tests and analytically validating multiple analytes.

Genotyping three SNPs affecting warfarin drug response by isothermal real-time HDA assays

BACKGROUND

The response to the anticoagulant drug warfarin is greatly affected by genetic polymorphisms in the VKORC1 and CYP2C9 genes. Genotyping these polymorphisms has been shown to be important in reducing the time of the trial and error process for finding the maintenance dose of warfarin thus reducing the risk of adverse effects of the drug.

METHOD

We developed a real-time isothermal DNA amplification system for genotyping three single nucleotide polymorphisms (SNPs) that influence warfarin response. For each SNP, real-time isothermal Helicase Dependent Amplification (HDA) reactions were performed to amplify a DNA fragment containing the SNP. Amplicons were detected by fluorescently labeled allele specific probes during real-time HDA amplification.

RESULTS

Fifty clinical samples were analyzed by the HDA-based method, generating a total of 150 results. Of these, 148 were consistent between the HDA-based assays and a reference method. The two samples with unresolved HDA-based test results were repeated and found to be consistent with the reference method.

CONCLUSION

The HDA-based assays demonstrated a clinically acceptable performance for genotyping the VKORC1 -1639G>A SNP and two SNPs (430C>T and 1075A>C) for the CYP2C9 enzyme (CYP2C9*2 and CYP2C9*3), all of which are relevant in warfarin pharmacogenentics.

Aberrant regulation of endogenous ouabain-like factor in bipolar subjects

Ill phases of bipolar illness are associated with abnormalities in ion regulation and intracellular ion concentrations. Previously, it has been reported that mania is characterised by lower circulating levels of ion regulating endogenous cardenolides, and that bipolar subjects lack the normal seasonal variation of these factors. Since endogenous cardenolides are elaborated in settings of extensive physical activity, euthymic bipolar and psychiatrically normal control subjects were asked to exercise to exhaustion. Plasma concentrations of endogenous cardenolides were measured at baseline, 60 min, peak exercise and post-recovery. Ouabain-like immunoreactive factor (OLF) was lower at baseline (0.005+/-S.D. 0.01 ng/mL in bipolar vs. 0.072+/-0.06 ng/mL in normal control subjects, P=0.019), lower at 60 min (0.007+/-S.D. 0.02 ng/mL in bipolar vs. 0.075+/-0.06 ng/mL in normal control subjects, P=0.029), and tended to be lower at peak exercise (0.009+/-S.D. 0.02 ng/mL in bipolar vs. 0.131+/-0.21 ng/mL in normal control subjects, P=0.15) in bipolar subjects compared to non-psychiatric controls. Other endogenous cardenolides did not vary significantly. The endogenous cardenolide, OLF, may be aberrantly controlled in bipolar illness.

Urinary proteins for the diagnosis of obstructive sleep apnea syndrome

Approximately 2-3% of all children in the United States suffer from obstructive sleep apnea (OSA). This condition is characterized by repeated events of partial or complete obstruction of the upper airways during sleep leading to recurring episodes of hypercapnia, hypoxemia, and arousal throughout the night as well as snoring, which afflicts 7-10% of all children. Since clinical history and physical examination are unreliable in the differentiation between children with OSA and children with primary snoring (PS) who have no apparent alteration in sleep architecture, current diagnostic approaches for OSA require an overnight sleep study (ONP). ONP is onerous, relatively unavailable, labor intensive, and inconvenient, leading to long waiting periods and unnecessary delays in diagnosis and treatment. Development of noninvasive biomarker(s) capable of reliably distinguishing children with PS from those with OSA would greatly facilitate timely screening and diagnosis of OSA in children. Therefore, we hypothesized that proteomic strategies in the urine may permit the identification of biomarker(s) that reliably screen for OSA. In this study, time-of-flight mass spectrometry was used to profile proteins in the first morning void urines from children. We discovered that urocortins are increased in OSA and provide a noninvasive approach for quick and convenient diagnosis otf OSA in snoring children.

Adiponectin Receptor-1 C-Terminal Fragment (CTF) in Plasma: Putative Biomarker for Diabetes

Introduction

Polypeptide fragments from cell surface receptors when found in plasma may be indicators of receptor regulation in disease conditions. It is known that subjects with diabetes have significantly lower plasma concentrations of adiponectin, a hormone released by adipose tissue, compared with nondiabetic controls. This hormone interacts with cell surface receptors in muscle (AdipoR1) and liver (AdipoR2).

Methods

We analyzed the relative distribution of specific fragments of AdipoR1 in healthy and diabetic individuals using an immunoaffinity mass spectrometry approach. We used antibodies raised against AdipoR1 immobilized on pre-activated protein chip surfaces to determine the molecular weights of bound polypeptide fragments using immunomass spectrometry (immuno-MS).

Results

Initially, immuno-MS analyses using a polyclonal antibody revealed two peaks (m/z 3,902 and 7,812) in plasma from normal, healthy individuals (n = 5) that were not present in the plasma of diabetics (n = 5). To confirm the detection of these fragments, a monoclonal antibody was developed against the last 25 amino acids of the AdipoR1 C-terminal fragment (CTF). Using the immuno-MS method, the monoclonal antibody detected the AdipoR1 CTF (m/z 3475) in all healthy controls (n = 10), but did not detect these fragments in the diabetic patients (n = 10).

Discussion

These preliminary observations suggest that the plasma levels of this receptor fragment may serve as an indicator of diabetic condition.

Catastrophic gastrointestinal injury due to battery acid ingestion

BACKGROUND

Acids account for 20% of all chemical exposures through various routes. Caustic acids such as hydrochloric and sulfuric acid are common ingredients in many household and industrial products. Due to the corrosive properties of these substances, tissue injury caused by oral exposure can lead to severe esophageal and gastrointestinal burns.

CASE REPORT

We report a case of a patient presenting with severe acidosis, who required multiple laparoscopic evaluations to assess various gastrointestinal tract injuries and who ultimately underwent total gastrectomy. The diagnosis was made primarily based on the arterial blood gas and esophagogastroduodenoscopy findings, as well as the pathological examinations of various biopsied and resected tissues showing hemorrhagic necrosis of the esophagus, stomach, and small bowel. This patient eventually admitted to having ingested an unspecified amount of battery acid.

CONCLUSIONS

Collaborative efforts by Emergency Medicine, Pathology, and General Surgery services are required for timely diagnosis, treatment, and management of patients after caustic acid exposures.

Immunological evaluation of urinary trypsin inhibitors in blood and urine: role of N- & O-linked glycoproteins

Urinary trypsin inhibitors (uTi) suppress serine proteases during inflammation. After liberation from proinhibitors (P-alpha-I and I-alpha-I) by the white blood cell (WBC) response, uTi readily pass through the kidneys into urine. A key uTi, bikunin, is attached to O-linked and N-linked glycoconjugates. Recently, uTi inhibitors, called uristatins, were found to lack the O-linked glycoconjugates. Monoclonal antibodies were produced using purified uristatin and screened for binding differences to uristatin, bikunin, P-alpha-I, and I-alpha-I. Antibody-binding patterns were characterized using immunoaffinity binding onto protein-chip surfaces and analysis by Surface Enhanced Laser Desorption/Ionization mass spectrometry (SELDI), using specimens from patients and from purified uTi standards. Antibodies were developed and used in an enzyme-linked immunosorbent assay (ELISA) method for uTi measurement in urine and plasma specimens. ELISA was performed on specimens from normal, presumed healthy, controls and from patients who had been screened for inflammation using a high sensitivity C-reactive protein (CRP) test and a complete blood count (CBC). Polyclonal antibody against uTi showed cross-reactivity with the Tamm-Horsfall protein (THP) and with proinhibitors. Screening of anti-uTi monoclonal antibodies (Mab) revealed antibodies that did not cross-react with either of the above, thus providing a tool to measure both uristatin and bikunin in urine with Mab 3G5 and in plasma with Mab 5D11. The monoclonal antibody 5D11 cross-reacts with specific N-linked glycoconjugates of uristatin present in plasma. In ca 96% of healthy adults, uTi were present at <12 mg/l in urine and <4 mg/l in plasma. We also found that patients with an inflammation and a CRP of >2.0 mg/l had higher urinary concentrations of uTi than the control population in every subject. Free uristatin and bikunin pass readily into urine and are primarily bound to heavy chains that constitute the proinhibitor form in plasma.

Bikunin (Urinary Trypsin Inhibitor): Structure, Biological Relevance, And Measurement

Inflammatory processes, such as phagocytosis, coagulation, and vascular dilation, promote the release of serine proteases by neutrophils, macrophages, mast cells, lymphocytes, and the epithelial or endothelial cells. These proteases further facilitate the release of inflammatory cytokines and growth factors as well as take part in signal-cell proliferation through protease-activated receptors (PARs). Controlling the action of this cascade is necessary to prevent further damage to the normal tissues. One of the main anti-inflammatory response mediators is bikunin (Bik) that is responsible for inhibiting the activity of many serine proteases such as trypsin, thrombin, chymotrypsin, kallikrein, plasmin, elastase, cathepsin, Factors IXa, Xa, XIa, and XlIa. During the acute-phase response, Bik is released into plasma from proinhibitors primarily due to increased elastase activity. Bik is a glycoprotein, also referred to as urinary trypsin inhibitor, which in plasma inhibits the trypsin family of serine proteases by binding to either of the two Kunitz-binding domains. Bik also accumulates in urine. In conditions such as infection, cancer, tissue injury during surgery, kidney disease, vascular disease, coagulation, and diabetes, the concentrations of Bik in plasma and urine are increased. Several trypsin inhibitory assays for urine and immunoassays for both blood and urine have been described for measuring Bik. In addition to presenting the synthesis, structure, and pathophysiology of Bik, we will summarize various diagnostic approaches for measuring Bik. Analysis of Bik may provide a rapid approach in assessing various conditions involving the inflammatory processes.

Analysis of ligand binding by bioaffinity mass spectrometry

BACKGROUND

Ligand binding is commonly analyzed using various immunoassays that are generally time-consuming and some may require secondary antibodies or gel electrophoresis which are also time-consuming and sometimes subjective. We introduced various examples for a more rapid approach using pre-activated surface chips which are analyzed by surface enhanced laser desorption/ionization-time of flight mass spectrometry (SELDI-TOF MS). Specific applications presented in this study include immobilization of antigen, antibody or oligo DNA on pre-activated chips with subsequent identification of the binding antibodies, antigens or DNA binding proteins to demonstrate the universal utility of this novel approach.

METHODS

BSA-digoxin conjugate (BSA-Dig), anti-digoxin antibody, anti-urinary trypsin inhibitor (uTi) antibody, or a double stranded oligo nucleotide based on the nucleotide sequence between -91 and -10 of the human CYP 450 2E1 promoter were immobilized on the Ciphergen pre-activated surface chips. Anti-digoxin antibody, BSA-digoxin conjugate, uTi, and CYP450 2E1 promoter binding protein were captured on the chip and identified by SELDI-TOF MS.

RESULTS

A protein with 141kDa was identified from anti-digoxin serum using BSA-Dig chips. This binding was competitively inhibited by addition of digoxin. Using anti-digoxin antibody, a peak at approximately 66kDa was detected in the preparation of BSA-Dig. This peak was also inhibited by free digoxin, suggesting BSA-Dig is detected. uTi fragments with approximately 3kDa to approximately 30kDa in the standard and urine samples were captured on the chip by anti-uTi antibody. Finally, we identified a 95-kDa CYP 450 2E1 promoter binding protein in HeLa cells nuclear extracts.

CONCLUSIONS

Bioaffinity SELDI-TOF MS is a powerful and versatile approach for analysis of ligands. It eliminates tracer-labeled secondary antibodies and allows for determination of molecular weights of binding proteins and their ligands directly. This approach may also be considered for the detection of enzymes, receptors, or any other specific ligands.

Application of bioaffinity mass spectrometry for analysis of ligands

Bioaffinity mass spectrometry is a novel technology for analysis of binding proteins and their ligands. In this review, we introduce the concepts and principles of bioaffinity surface-enhanced laser desorption/ionization-time of flight mass spectrometry (SELDI-TOF MS). Various preactivated chip types and several approaches for binding of ligands or their binders to the chips are discussed. We also provide specific examples for the use of this technology for screening antibodies, analyzing ligands, glycoconjugates, protein-protein inter-actions, and DNA (RNA) binding proteins. In pursuit of developing new tests or studies of mechanism of drug action in therapeutic drug monitoring practice, this technology may provide a more rapid approach for ligand-binder studies.

Proteomics: a new diagnostic frontier

BACKGROUND

Analysis of proteins has been an integral part of the field of clinical chemistry for decades. Recent advances in technology and complete identification of the human genome sequence have opened up new opportunities for analysis of proteins for clinical diagnostic purposes.

METHODS

Content of a recent conference of proteomics is summarized.

RESULTS

New analytical methods allow the simultaneous analysis of a large number of proteins in biological fluids such as serum and plasma, offering partial views of the complete set of proteins or proteome. Plasma presents many analytical challenges, such as the complexity of components, predominance of a few major components, and the large concentration range of components, but the number of proteins that can be detected in plasma has expanded dramatically from hundreds to thousands. At the same time, there is increased capability to detect structural variations of proteins. Recent studies also identified the presence of complex sets of small protein fragments in plasma. This set of protein fragments, the fragmentome or peptidome, is potentially a rich source of information about physiologic and disease processes.

CONCLUSIONS

Advances in proteomics offer great promise for the discovery of markers that might serve as the basis for new clinical laboratory tests. There are many challenges, however, in the translation of newly discovered markers into clinical laboratory tests.

Serum proteomic patterns associated with sleep-disordered breathing in children

Obstructive sleep apnea (OSA) is a major public health problem affecting approximately 2% to 3% of children. However, snoring, the cardinal symptom of OSA, affects at least 5-fold more children, such that evaluation by overnight polysomnography (ONP) is required for the diagnosis. ONP is laborious, expensive, and relatively unavailable to children. Proteomic mass spectrometry coupled with bioinformatic tools provide valuable means for discovery of new biomarkers in serum for a variety of human disorders. The possibility exists that snoring children with and without OSA may exhibit different protein expression profiles in serum that could be useful in the development of novel diagnostic tools for this condition. The proteomic patterns of 20 children with OSA and of 20 children with habitual primary snoring but no evidence of OSA (HS) were evaluated using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS). Linear discriminative analysis identified three differentially regulated proteins with molecular masses of 5896, 3306, 6068 Da that were capable of diagnosing OSA with 93% sensitivity and 90% specificity. Thus, the proteomic signatures of sera from children with OSA differ from those of HS who do not fulfill the current criteria for treatment. Identification and sequencing of those differentially expressed proteins discovered through proteomic strategies may lead to future development of serum-based diagnostic tests for OSA in snoring children.

Sensitive noninvasive marker for the diagnosis of probable bacterial or viral infection

Urinary trypsin inhibitor (uTi) is a product of elastase-mediated degradation of interleukin-alpha-inhibitor (I-alpha-I). Its activity increases in the urine of patients with a malignancy, inflammation, or infection, or in late pregnancy. The objective of this study was to compare the sensitivity of uTi in urine with that of serum quantitative C-reactive protein (CRP) for diagnosing infection, as indicated by white cell response and clinical assessment. Ninety controls and 171 patients with various systemic infections were enrolled. We measured uTi enzymatically on a Cobas Fara (Roche Diagnostics). Patients were separated into bacterial, probable bacterial, viral, or probable viral groups based on the results of a complete blood count with differential (CBC), urinalysis (UA), and clinical assessment. In the bacterial (n=70) and control (n=90) groups, the uTi values (mean+/-SE) were 25.3+/-3.1 mg/L and 2.8+/-0.8 mg/L, respectively. uTi (at 2.7 mg/L) had a diagnostic sensitivity of 91% and specificity of 82% (AUC=0.889), whereas CRP (at a cutoff of 10 mg/L) had a sensitivity and specificity of 82% and 96%, respectively (AUC=0.921). As a marker of infection (positive in both bacterial and viral groups), uTi had a sensitivity of 91% (AUC=0.884) vs. 89% (AUC=0.828) for CRP. Our data indicate that uTi has sufficient clinical sensitivity for screening systemic infections, and may have diagnostic value as a noninvasive test.

Multicenter evaluation of the performance characteristics of the bayer VERSANT HCV RNA 3.0 assay (bDNA)

In this multicenter evaluation, the VERSANT HCV RNA 3.0 Assay (bDNA) (Bayer Diagnostics, Tarrytown, N.Y.) was shown to have excellent reproducibility, linearity, and analytical sensitivity across specimen collection matrices (serum, EDTA, ACD-A), and hepatitis C virus (HCV) genotypes 1 to 6. The VERSANT HCV bDNA Assay has a reportable range of 615 to 7690000 (7.69 x 10(6)) IU/ml. The total coefficient of variation (CV) ranged from 32.4% at 615 IU/ml to 17% at 6.8 x 10(6) IU/ml. The assay was linear across the reportable range. Analytical specificity of 98.8% was determined by testing 999 specimens from volunteer blood donors. Evaluation of HCV genotypes using RNA transcripts of representative clones of 1a, 1b, 2a, 2b, 2c, 3a, 4a, 5a, and 6a and patient specimens showed that the largest difference between genotype 1, upon which the assay is standardized, and non-1 genotypes was within 1.5-fold. Testing of potentially interfering endogenous substances and exogenous substances and conditions found no interference in HCV-positive or HCV-negative specimens except for unconjugated bilirubin at concentrations of >or=20 mg/dl and protein at concentrations of >or=9 g/dl. Biological variability was estimated from 29 clinically stable individuals not on HCV therapy who were tested weekly over an 8-week period. The combined estimate of total (biologic plus assay) variability was 0.15 log(10) standard deviation (CV, 36.1%), a fold change of 2.6. Thus, the observed fold change between any two consecutive HCV RNA measures is expected to be less than 2.6-fold (equivalent to 0.41 log(10) IU/ml) 95% of the time in clinically stable individuals.

The uristatin dipstick is useful in distinguishing upper respiratory from urinary tract infections

BACKGROUND

We determined the diagnostic value of the trypsin inhibitor, uristatin, that is commonly found in urine and plasma in patients with infections or inflammations of any kind.

METHODS

We collected urine specimens from patients with infections of the urinary or upper respiratory tract and from healthy controls. We also collected blood from patients with a likely upper respiratory tract infection and healthy controls. A bacterial count of >10(5) organisms/ml in urine was considered to represent infection rather than contamination.

RESULTS

The uristatin dipstick test in urine showed acceptable negative predictive values (NPV of up to 93%) for patients without infection or inflammation. Here, the dipsticks could eliminate some urine cultures. For those with infection or inflammation, the positive predictive values (PPV) of the dipsticks were lower (up to 57%). Including the leukocyte esterase and nitrite values increased the PPV of the dipsticks for those with disease.

CONCLUSIONS

The uristatin strip was more accurate than the leukocyte and nitrite dipsticks for predicting upper respiratory infections (URI) and C-reactive protein for those with infection or inflammation. The uristatin dipstick was able to detect both the bikunin and uristatin inhibitors.

Strategies for developing biomarkers of heart failure

BACKGROUND

Heart failure (HF) is a devastating disease with increasing prevalence in elderly populations. One-half of all patients die within 5 years of diagnosis. The annual cost of treating patients with HF in the US is more than $20 billion, which is estimated to be greater than that of myocardial infarction and all cancers combined. Given the complex pathophysiology and varied manifestations of HF, interest has intensified in developing biological markers to predict susceptibility and aid in the early diagnosis and management of this disease.

METHODS

We searched Medline via Ovid for studies published during the period 1966-2003 regarding various biomarkers suggested for HF. Our review focused on developing strategies for discovering and using new biomarkers, particularly those potentially linked to pathophysiologic mechanisms. We also point out strategic advantages, limitations, and methods available for measuring each of the currently proposed markers.

RESULTS

Biomarkers reviewed include those released from the heart during normal homeostasis (natriuretic peptides), those produced elsewhere that act on the heart (endogenous cardiotonic steroids and other hormones), and those released in response to tissue damage (inflammatory cytokines). The concept of using a combination of multiple markers based on diagnosis, prognosis, and acute vs chronic disease is also discussed. In view of recent advances in our understanding of molecular biochemical derangements observed during cardiac failure, we consider the concept of myocardial remodeling and the heart as part of an endocrine system as strategies.

CONCLUSION

Strategically, biomarkers linked to mechanisms involved in the etiology of HF, such as dysregulation of ion transport, seem best suited for serving as early biological markers to predict and diagnose disease, select therapy, or assess progression.

What is next in pharmacogenomics? Translating it to clinical practice

Pharmacogenomics (PG) holds promise for transforming medical therapeutics but the details of how the promise will become reality are still vague. In this article, we focus on the role that laboratory medicine, as a discipline, might play in transitioning the application of pharmacogenomics into the healthcare system and begin to frame a perspective on how PG may be viewed in this context. Development of clinical diagnostic tests usually evolves as a continuum of information starting with the discovery of a potential biological marker through to its routine use in clinical practice. This process has traditionally been rooted in the practice of laboratory medicine and, importantly, includes the development of testing strategies to optimize the predictive value of single or a combination of biological markers. In this context, we also discuss a perspective on some future strategies that may prove useful in advancing the application of PG, including the need for an evidenced-based approach and the potential role of proteomics as a means to drive more comprehensive strategies.

Cardioactive steroid poisoning from an herbal cleansing preparation

We describe a case of unintentional poisoning from a cardioactive steroid and the subsequent analytic investigation. A 36-year-old woman with no past medical history and taking no conventional medications ingested an herbal preparation marketed for "internal cleansing." Its ingredients were neither known to the patient nor listed on the accompanying literature. The next morning, nausea, vomiting, and weakness developed. In the emergency department, her blood pressure was 110/60 mm Hg, and her pulse rate was 30 beats/min. Her ECG revealed a junctional rhythm at a rate of 30 beats/min and a digitalis effect on the ST segments. After empiric therapy with 10 vials of digoxin-specific Fab (Digibind), her symptoms resolved, and she reverted to a sinus rhythm at a rate of 68 beats/min. Her serum digoxin concentration measured by means of the fluorescence polarization immunoassay (Abbott TDx) was 1.7 ng/mL. Further serum analysis with the Tina Quant digoxin assay, a more digoxin-specific immunoassay, found a concentration of 0.34 ng/mL, and an enzyme immunoassay for digitoxin revealed a concentration of 20 ng/mL (therapeutic range 10 to 30 ng/mL). Serum analysis by means of high-performance liquid chromatography revealed the presence of active digitoxin metabolites; the parent compound was not present. When the diagnosis of cardioactive steroid poisoning is suspected clinically, laboratory analysis can confirm the presence of cardioactive steroids by using immunoassays of varying specificity. An empiric dose of 10 vials of digoxin-specific Fab might be beneficial in patients poisoned with an unknown cardioactive steroid.

Mammalian cardenolides as biomarkers in congestive heart failure

Congestive heart failure (CHF) afflicts over 5 million individuals in the United States, and most die within 5 yr of diagnosis. Because of the high morbidity and mortality associated with CHF, the search for biomarkers to predict, diagnose, and manage this disease has intensified. Calcium homeostasis and alterations in intracellular concentrations of this cation have been implicated in both hypertrophy as well as the adaptive mechanisms observed in CHF. In this article, we discuss the roles of the sodium pump and the endogenous mammalian cardenolides and their involvement in the pathophysiology of this disease in view of the regulation of intracellular calcium. Understanding the mechanisms for the release of mammalian cardenolides in plasma, the alterations in sodium pump isoforms and function, and the modulation of pathways involving calcium in hypertrophy and CHF may assist in the development of new biological markers capable of predicting the disease before significant progression and irreversible heart failure.

Digoxin and its related endogenous factors

The digitalis drugs are plant-derived cardenolide compounds used medicinally for several hundred years. These drugs elicit inotropic and chronotropic effects on the heart, but they also affect many other tissues. The mechanism of action involves inhibition of the ion-transport activity of a membrane-associated protein called Na, K-ATPase (sodium pump). Present theory holds that the sodium pump is the principal molecular receptor for the digitalis drugs. Recent evidence indicates the presence of naturally occurring digitalis-like compounds in mammals. It is believed these compounds, collectively known as either digitalis-like (DLF) or ouabain-like (OLF) factors, may be endogenous hormones regulating the biological activity of the sodium pump and its isoforms. The presence of deglycosylated and other congeners of one specific DLF, the digoxin-like immunoreactive factor (DLIF), has very recently been described in humans. Digoxin as a drug is the most widely prescribed digitalis in the U.S., and its measurement in serum has established a model for present-day therapeutic drug monitoring (TDM). Historically, the accurate measurement of digoxin in blood has been difficult. This article focuses on the present understanding of the clinical use of digoxin, factors that affect the accuracy of measuring digoxin, the principle of measuring metabolically active species of digoxin, and the effects of DLIF and other interfering substances in digoxin immunoassay.

The Role of the Clinical Laboratory in Managing Chemical or Biological Terrorism

Background: Domestic and international acts of terrorism using chemicals and pathogens as weapons have recently attracted much attention because of several hoaxes and real incidents. Clinical laboratories, especially those affiliated with major trauma centers, should be prepared to respond rapidly by providing diagnostic tests for the detection and identification of specific agents, so that specific therapy and victim management can be initiated in a timely manner. As first-line responders, clinical laboratory personnel should become familiar with the various chemical or biological agents and be active participants in their local defense programs.

Approach: We review the selected agents previously considered or used in chemical and biological warfare, outline their poisonous and pathogenic effects, describe techniques used in their identification, address some of the logistical and technical difficulties in maintaining such tests in clinical laboratories, and comment on some of the analytical issues, such as specimen handling and personal protective equipment.

Content: The chemical agents discussed include nerve, blistering, and pulmonary agents and cyanides. Biological agents, including anthrax and smallpox, are also discussed as examples for organisms with potential use in bioterrorism. Available therapies for each agent are outlined to assist clinical laboratory personnel in making intelligent decisions regarding implementation of diagnostic tests as a part of a comprehensive defense program.

Summary: As the civilian medical community prepares for biological and chemical terrorist attacks, improvement in the capabilities of clinical laboratories is essential in supporting counterterrorism programs designed to respond to such attacks. Accurate assessment of resources in clinical laboratories is important because it will provide local authorities with an alternative resource for immediate diagnostic analysis. It is, therefore, recommended that clinical laboratories identify their current resources and the extent of support they can provide, and inform the authorities of their state of readiness.

The role of the clinical laboratory in managing chemical or biological terrorism

BACKGROUND

Domestic and international acts of terrorism using chemicals and pathogens as weapons have recently attracted much attention because of several hoaxes and real incidents. Clinical laboratories, especially those affiliated with major trauma centers, should be prepared to respond rapidly by providing diagnostic tests for the detection and identification of specific agents, so that specific therapy and victim management can be initiated in a timely manner. As first-line responders, clinical laboratory personnel should become familiar with the various chemical or biological agents and be active participants in their local defense programs.

APPROACH

We review the selected agents previously considered or used in chemical and biological warfare, outline their poisonous and pathogenic effects, describe techniques used in their identification, address some of the logistical and technical difficulties in maintaining such tests in clinical laboratories, and comment on some of the analytical issues, such as specimen handling and personal protective equipment.

CONTENT

The chemical agents discussed include nerve, blistering, and pulmonary agents and cyanides. Biological agents, including anthrax and smallpox, are also discussed as examples for organisms with potential use in bioterrorism. Available therapies for each agent are outlined to assist clinical laboratory personnel in making intelligent decisions regarding implementation of diagnostic tests as a part of a comprehensive defense program.

SUMMARY

As the civilian medical community prepares for biological and chemical terrorist attacks, improvement in the capabilities of clinical laboratories is essential in supporting counterterrorism programs designed to respond to such attacks. Accurate assessment of resources in clinical laboratories is important because it will provide local authorities with an alternative resource for immediate diagnostic analysis. It is, therefore, recommended that clinical laboratories identify their current resources and the extent of support they can provide, and inform the authorities of their state of readiness.

Standardizing utilization of biomarkers in diagnosis and management of acute cardiac syndromes

Publications on the development and use of myocardial markers have exploded in the decade of the 1990s. According to subscriptions to proficiency testing surveys, enzymatic measurement of creatine kinase and lactate dehydrogenase isoenzymes have largely been replaced by CK-MB mass immunoassays. Laboratories reporting use of myoglobin and cardiac troponin have increased tremendously over the past few years. In this field of medicine where there have been dramatic changes, development of consensus guidelines can be helpful to provide assistance to clinicians and laboratorians as to how they can make the best use of new cardiac markers for clinical practice.

Validity of unbound digoxin measurements by immunoassays in presence of antidote (Digibind)

Measurement of unbound digoxin in presence of Fab fragments may be useful in management of overdoses. The analysis can be performed on serum directly or on ultrafiltrate of serum. The architecture of the immunoassay may influence the validity of results obtained using these two approaches. We tested this hypothesis by preparing serum mixtures containing various concentrations of digoxin and Digibind and analyzed them by the immunoassays before and after ultrafiltration. Four samples collected from Digibind-treated patients were also analyzed before and after ultrafiltration. The slopes and the y-intercepts of the measured versus the expected values for serum and its ultrafiltrate overlapped for the MEIA digoxin assay. For other three immunoassays tested (ACS:180, Stratus, and On-Line), either the slope or the intercept for measured versus the expected results for serum were significantly different (P < 0.05) than those for ultrafiltrate. Following addition of digoxin and Digibind, differences in results for serum analyzed directly or after ultrafiltration were < 0.50 ng/ml. Comparable samples from digoxin-overdosed patients treated with Digibind had differences of > 1.0 ng/ml. Previous claims reporting direct analysis of digoxin in presence of antidote but not having used patient samples for validation should be revisited. To date, analysis of serum ultrafiltrate by an immunoassay proven not to have matrix bias remains the most accurate approach in measuring unbound digoxin in presence of antidote.

Simultaneous Rapid Measurement of Whole Blood Myoglobin, Creatine Kinase MB, and Cardiac Troponin I by the Triage Cardiac Panel for Detection of Myocardial Infarction

This multicenter study evaluated the Biosite Triage® Cardiac Panel as a quantitative, multimarker, whole blood system for the detection of acute myocardial infarction (MI). Optimum cutoffs for the discrimination of acute MI (n = 192 patients, 59 with MI) as determined by ROC curve analyses were as follows: 0.4 μg/L for cardiac troponin I (cTnI); 4.3 μg/L for the creatine kinase MB isoenzyme (CK-MB); and 107 μg/L for myoglobin. The Triage Panel showed the following concordances for detection or rule-out of MI compared with established devices: cTnI &gt;89%; CK-MB &gt;81%; myoglobin &gt;69%. No significant differences were present between methods for the same marker. Diagnostic efficiencies demonstrated comparable sensitivities and specificities for the diagnosis of MI in patients presenting with symptoms compared with the Dade, Beckman, and Behring CK-MB, cTnI, and myoglobin assays; the ratio of sensitivity to specificity for each marker was as follows: cTnI, 98%:100%; CK-MB, 95%:91%; myoglobin, 81%:92%. The areas under the ROC curves for the Biosite myoglobin, CK-MB, and cTnI were 0.818, 0.905, and 0.970, respectively; the areas were significantly different, P &lt;0.05. In patients with skeletal muscle injury and renal disease, the Triage cTnI showed 94% and 100% specificity, respectively. The Triage panel offers clinicians a whole blood, point-of-care analysis of multiple cardiac markers that provides excellent clinical sensitivity and specificity for the detection of acute MI.

Simultaneous rapid measurement of whole blood myoglobin, creatine kinase MB, and cardiac troponin I by the triage cardiac panel for detection of myocardial infarction

This multicenter study evaluated the Biosite Triage(R) Cardiac Panel as a quantitative, multimarker, whole blood system for the detection of acute myocardial infarction (MI). Optimum cutoffs for the discrimination of acute MI (n = 192 patients, 59 with MI) as determined by ROC curve analyses were as follows: 0.4 microgram/L for cardiac troponin I (cTnI); 4.3 microgram/L for the creatine kinase MB isoenzyme (CK-MB); and 107 microgram/L for myoglobin. The Triage Panel showed the following concordances for detection or rule-out of MI compared with established devices: cTnI >89%; CK-MB >81%; myoglobin >69%. No significant differences were present between methods for the same marker. Diagnostic efficiencies demonstrated comparable sensitivities and specificities for the diagnosis of MI in patients presenting with symptoms compared with the Dade, Beckman, and Behring CK-MB, cTnI, and myoglobin assays; the ratio of sensitivity to specificity for each marker was as follows: cTnI, 98%:100%; CK-MB, 95%:91%; myoglobin, 81%:92%. The areas under the ROC curves for the Biosite myoglobin, CK-MB, and cTnI were 0.818, 0.905, and 0.970, respectively; the areas were significantly different, P <0.05. In patients with skeletal muscle injury and renal disease, the Triage cTnI showed 94% and 100% specificity, respectively. The Triage panel offers clinicians a whole blood, point-of-care analysis of multiple cardiac markers that provides excellent clinical sensitivity and specificity for the detection of acute MI.