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.

Validation of cell-cycle arrest biomarkers for acute kidney injury using clinical adjudication.

RATIONALE: We recently reported two novel biomarkers for acute kidney injury (AKI), tissue inhibitor of metalloproteinases (TIMP)-2 and insulin-like growth factor binding protein 7 (IGFBP7), both related to G1 cell cycle arrest. OBJECTIVES: We now validate a clinical test for urinary [TIMP-2]·[IGFBP7] at a high-sensitivity cutoff greater than 0.3 for AKI risk stratification in a diverse population of critically ill patients. METHODS: We conducted a prospective multicenter study of 420 critically ill patients. The primary analysis was the ability of urinary [TIMP-2]·[IGFBP7] to predict moderate to severe AKI within 12 hours. AKI was adjudicated by a committee of three independent expert nephrologists who were masked to the results of the test. MEASUREMENTS AND MAIN RESULTS: Urinary TIMP-2 and IGFBP7 were measured using a clinical immunoassay platform. The primary endpoint was reached in 17% of patients. For a single urinary [TIMP-2]·[IGFBP7] test, sensitivity at the prespecified high-sensitivity cutoff of 0.3 (ng/ml)(2)/1,000 was 92% (95% confidence interval [CI], 85-98%) with a negative likelihood ratio of 0.18 (95% CI, 0.06-0.33). Critically ill patients with urinary [TIMP-2]·[IGFBP7] greater than 0.3 had seven times the risk for AKI (95% CI, 4-22) compared with critically ill patients with a test result below 0.3. In a multivariate model including clinical information, urinary [TIMP-2]·[IGFBP7] remained statistically significant and a strong predictor of AKI (area under the curve, 0.70, 95% CI, 0.63-0.76 for clinical variables alone, vs. area under the curve, 0.86, 95% CI, 0.80-0.90 for clinical variables plus [TIMP-2]·[IGFBP7]). CONCLUSIONS: Urinary [TIMP-2]·[IGFBP7] greater than 0.3 (ng/ml)(2)/1,000 identifies patients at risk for imminent AKI. Clinical trial registered with www.clinicaltrials.gov (NCT 01573962).

Pesticide-induced quadriplegia in a 55-year-old woman.

Acephate is a commercial organophosphate pesticide formerly used in households and now used primarily for agriculture. Poisoning symptoms include salivation, lacrimation, urination, defecation, gastrointestinal illness, and emesis. In addition to these classic symptoms, neurodegeneration can result from increased and continued exposure of organophosphates. This 55-year-old woman presented with organophosphate-induced delayed neuropathy in the form of quadriplegia due to the commonly used pesticide acephate. She was exposed to this pesticide through multiple sprayings in her work office with underrecognized poisoning symptoms. She presented to her primary care physician with neuropathic pain and paralysis in her arm following the sprayings and eventual complete paralysis. The patient lived for 2 years following her toxic exposure and quadriplegia. A complete autopsy after her death confirmed a transverse myelitis in her spinal cord. We conclude that in susceptible individuals, acephate in excessive amounts can produce severe delayed neurotoxicity as demonstrated in animal studies.

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.

Therapeutic monitoring of opioids: a sensitive LC-MS/MS method for quantitation of several opioids including hydrocodone and its metabolites.

For pain management, opioid therapy is a mainstay for treating acute pain and relieving moderate to severe chronic pain. Quantitative measurement of opioids and their metabolites in urine is used mainly for confirmation of screened results obtained for clinical and forensic purposes. Due to limitations in interpretation of urine results for pain management testing purposes, the use of blood or serum to assess opioids and their metabolites may be of benefit. This report describes a sensitive liquid chromatography-tandem mass spectrometry method for the detection of hydrocodone and its metabolites hydromorphone, norhydrocodone, and dihydrocodeine, and other common opiates that patients may be taking, including morphine, codeine, oxycodone, and oxymorphone in a single extraction. The method uses solid-phase extraction of 500 µL of sample with quantitation by liquid chromatography-tandem mass spectrometry. The assay is linear from 1.0 to 100 ng/mL and has a between-day coefficient of variation of <10%. The major advantage of this method is that a single extraction can detect hydrocodone and its metabolites and other opiates or opioids that patients frequently use simultaneously with hydrocodone.

Improved sensitivity for methotrexate analysis using enzyme multiplied immunoassay technique on the Siemens Viva-E instrument.

BACKGROUND: The available assay kit for methotrexate (MTX) using the Syva enzyme multiplied immunoassay technique (EMIT) reagents on the Siemens Viva-E instrument allows for the detection of MTX in serum or plasma to concentrations as low as 0.3 µmole/L. Current clinical decision points for MTX therapeutic drug monitoring and leucorvorin rescue exist at concentrations below that limit. OBJECTIVE: The goal of this study was to lower the limit of MTX quantitation to 0.05 µmole/L using the EMIT assay technology. METHODS: EMIT MTX assay parameters were modified on the Viva-E instrument to increase the sample volume, alter the calibration method, and employ an alternate calibrator set created to achieve lower detection. Intraassay and interassay precision was assessed for MTX controls. RESULTS: We observed a CV of 9.4% for intraassay precision with a bias of <0.01% and a CV of 15.7% for interassay precision with a bias of 22.5% for the 0.05 µmole/L control. Precision data for all other controls were <4%. The modified EMIT MTX assay and the unmodified approved assay were compared with a high sensitivity fluorescence polarization immunoassay method. Linear regression of correlation data revealed that both the modified and the commercial EMIT assays produced positive bias compared with the high sensitivity fluorescence polarization immunoassay method (y-int = 0.03 and 0.08, respectively). However, the modified EMIT assay had the best correlation in the low range (0.03-2 µmole/L). Additionally, endogenous and chemical interference testing demonstrated that the modified assay was not affected to a clinically significant extent. CONCLUSIONS: The described modifications have enhanced the sensitivity of the Syva EMIT assay for MTX measurements down to 0.05 µmole/L with acceptable precision that can be used in clinical practice for monitoring MTX therapy.

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.

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.

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.

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.

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.

Two-dimensional differential in-gel electrophoresis proteomic approaches reveal urine candidate biomarkers in pediatric obstructive sleep apnea.

RATIONALE: Sleep studies are laborious, expensive, inaccessible, and inconvenient for diagnosing obstructive sleep apnea (OSA) in children. OBJECTIVES: To examine whether the urinary proteome uncovers specific clusters that are differentially expressed in the urine of children with OSA. METHODS: Two-dimensional differential in-gel electrophoresis (2D-DIGE) and mass spectrometry proteomics followed by validation with western blot of ELISA. MEASUREMENTS AND MAIN RESULTS: Morning urine proteins from 60 children with polysomnographically confirmed OSA and from matched children with primary snoring (n = 30) and control subjects (n = 30) were assessed. A total of 16 proteins that are differentially expressed in OSA were identified, and 7 were confirmed by either immunoblots or ELISA. Among the latter, receiver-operator curve analyses of urinary concentrations of uromodulin, urocortin-3, orosomucoid-1, and kallikrein assigned favorable predictive properties to these proteins. Furthermore, combinatorial approaches indicated that the presence of values beyond the calculated cutoff concentrations for three or more of the proteins yielded a sensitivity of 95% and a specificity of 100%. CONCLUSIONS: Proteomic approaches reveal that pediatric OSA is associated with specific and consistent alterations in urinary concentrations of specific protein clusters. Future studies aiming to validate this approach as a screening method of habitually snoring children appears warranted.

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.

Long interspersed nuclear element-1 mobilization as a target in cancer diagnostics, prognostics and therapeutics.

Long Interspersed Nuclear Element-1 (LINE-1) are DNAs that compromise 17% of our genome. LINE-1 expression is triggered by environmental stressors and accomplished through its demethylation leading to genomic instability. Expression of LINE-1 is regulated in adult somatic tissues through several endogenous defensive mechanisms, but is found to be associated with tumorigenesis in several cancers. This finding, has inspired the use of different indicators of LINE-1 activation, as biomarkers in cancer diagnostics and even therapeutic targets in recent years. The objective of this review is to provide a critical examination of LINE-1 elements as companion cancer diagnostic/prognostic biomarkers and anti-cancer drug targets. In our view, there's great potential for LINE-1 serving at both forefronts, but there is a need for more mechanistic studies in the clinic as well as on the bench research to validate LINE-1 activation elements as cancer biomarkers or therapeutic targets; in different cancer types and/or stages of the disease. In this context, development of minimally invasive, reliable and sensitive diagnostic tools for LINE-1 activation elements for clinical use, is of priority.

Discovery of the Long Interspersed Nuclear Element-1 activation product [Open Reading Frame-1 (ORF1) protein] in human blood.

Long Interspersed Nuclear Element 1 is the only autonomous mobile DNA capable of self-propagation, and is an environmental biomarker that is activated upon an environmental trigger. We have developed an ELISA method to detect and measure Open Reading Frame-1 (ORF1) and have applied it to interrogate serum samples from men with equivocal prostate specific antigen (PSA) results. Polyclonal antibodies were developed using the first 14-amino acid peptide of N-terminal-ORF1 protein. Remnant serum samples from a total of 53 men, ages>50 yr, were analyzed for immunoreactive ORF1 (iORF1) and PSA concentrations; outcomes for the non-biopsied and biopsied groups were also recorded. The dynamic range of the ELISA was between (CV): 2.0 (14%) to 30 ng/mL (1.2%). The total imprecision (within-run/inter-day) was: QC3 = 2.7%/21%, QC6 = 1.1%/18%, and QC20 = 0.33%/11%. The median iORF1 concentration in the non-biopsy group was 14.7 ng/mL (Q1 - Q3: 10.5 - Q3:18.4), which was significantly lower than the Biopsy group at 25.0 ng/mL (Q1 - Q3: 20.0-33.1), P-value = .003. In conclusion, we have developed a competitive ELISA and discovered the presence of iORF1 in serum, which could be used to advance future studies involving ORF1 measurement from blood. In addition, iORF1 may be a complement with the PSA screen to better detect prostate cancer.

Analytical interference of HBOC-201 (Hemopure, a synthetic hemoglobin-based oxygen carrier) on four common clinical chemistry platforms.

BACKGROUND: There are 13 million blood transfusions each year in the US. Limitations in the donor pool, storage capabilities, mass casualties, access in remote locations and reactivity of donors all limit the availability of transfusable blood products to patients. HBOC-201 (Hemopure®) is a second-generation glutaraldehyde-polymer of bovine hemoglobin, which can serve as an "oxygen bridge" to maintain oxygen carrying capacity while transfusion products are unavailable. Hemopure presents the advantages of extended shelf life, ambient storage, and limited reactive potential, but its extracellular location can also cause significant interference in modern laboratory analyzers similar to severe hemolysis. METHODS: Observed error in 26 commonly measured analytes was determined on 4 different analytical platforms in plasma from a patient therapeutically transfused Hemopure as well as donor blood spiked with Hemopure at a level equivalent to the therapeutic loading dose (10% v/v). RESULTS: Significant negative error ratios >50% of the total allowable error (>0.5tAE) were reported in 23/104 assays (22.1%), positive bias of >0.5tAE in 26/104 assays (25.0%), and acceptable bias between -0.5tAE and 0.5tAE error ratio was reported in 44/104 (42.3%). Analysis failed in the presence of Hemopure in 11/104 (10.6%). Observed error is further subdivided by platform, wavelength, dilution and reaction method. CONCLUSION: Administration of Hemopure (or other hemoglobin-based oxygen carriers) presents a challenge to laboratorians tasked with analyzing patient specimens. We provide laboratorians with a reference to evaluate patient samples, select optimal analytical platforms for specific analytes, and predict possible bias beyond the 4 analytical platforms included in this study.

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.