Repeatability Of Test Results Research Articles

Measurement of covered curvature based on a tape of integrated accelerometers

Quantitative measurements of spinal curvature can indicate the health of the human musculoskeletal system. However, existing measurement techniques are not feasible for unexposed back. This study used accelerometers to develop a portable, noninvasive, nonradiative, and cost-efficient device to quantitatively measure spinal curvature in real time. The measurement accuracy is approximately 99% when measuring a ø200-mm circle. Compared with the results of the three-dimensional motion analysis system, the device exhibited curvature results that were highly consistent in the Bland-Altman test (cervical lordosis angle (CLA): r = 0.973, thoracic kyphosis angle (TKA): r = 0.993, lumbar lordosis angle (LLA): r = 0.961, and spinal alignment trendline (SAT): r = 0.978). Repeatability test results: CLA = 37.63 ± 2.24°, TKA = 32.48 ± 0.98°, and LLA = 15.64 ± 1.12°. Thus, the proposed device can provide accurate and reliable quantitative measurements and can be used for spinal curvature measurements in the supine position.

Impact resistance test system for the helmet based on a polyvinylidene fluoride piezoelectric sensor array

As the most commonly used personal protection equipment (PPE) in various production activities, the impact resistance of the helmet is of great importance. Referred to the conventional experimental method, this study constructs a helmet impact resistance test system with a polyvinylidene fluoride (PVDF) sensor array. Compared with the traditional test method, this study installed PVDF sensors on the contact surface between the headform and the helmet. The stress and its distribution on the headform are measured directly, which is helpful to evaluate the impact resistance of the helmet more accurately and comprehensively. Finally, the intra-group correlation coefficient (ICC) and the coefficient of variation (CV) of peak pressure of the repeated test results are calculated to evaluate the reliability of the test system, which shows high reliability. The test system is helpful for optimization of the helmet production design and further related research.

Strain Sweep Fatigue Testing of Sand Asphalt Mortar to Investigate the Effects of Sample Geometry, Binder Film Thickness, and Testing Temperature

This study evaluated the viscoelastic fatigue behavior of binder using strain sweep fatigue testing of cylindrical sand asphalt mortar (SAM) samples. The SAM samples can represent the realistic film thickness (such as 10–70 μm thick) of the binder in mixtures, while testing repeatability-efficiency can still be met as a result of the use of a standard sand as a load carrier between binder films. A proper testing protocol is still under development, and one of the unknowns in the field is a set of testing conditions that can provide repeatable and case-sensitive test results. Toward that end, SAM samples with different dosages of binder in three geometries were tested at varying temperatures in this study. A PG 64-34 binder was used, and a strain sweep test using a dynamic shear rheometer was conducted to compare the test results from the different cases. Four parameters resulting from the SAM testing were examined: two accounting for material linear viscoelastic behavior and two accounting for fatigue damage characteristics. The parameters were incorporated with statistical analyses to quantitatively evaluate data variability and sensitivity influenced by the binder film thickness, SAM specimen geometry, and testing temperature. The coefficient of variation was less than 20% for all the cases, which indicated the validity of the SAM method attempted in this study. Results also indicated that fatigue behavior was independent of the SAM geometries used in this study, while binder film thickness and testing temperature significantly affected test results.

A novel vertical stress-controlled apparatus for studying suffusion along horizontal seepage through soils

In this study, a novel apparatus was developed for the study of horizontal suffusion behavior of compacted soils under vertical stress. The apparatus consists of a permeameter chamber to accommodate specimen preparation and testing, a pressurized water supply system to generate horizontal seepage flow, a vertical loading system to apply and maintain the vertical stress onto the specimen, a pore water pressure measuring system and a soil–water collection system both to capture the characteristics of the suffusion. The apparatus is featured with a tailor-made flexible pressure bladder for vertical stress control and a modified vacuumizing method for specimen saturation. It has been verified to well perform during the horizontal suffusion, in terms of the specimen uniformity and repeatability of test results. Preliminary tests with this apparatus have been carried out to investigate the suffusion behavior of a gap-graded cohesionless soil. It can be found that suffusion can heterogenize the soil specimen along the seepage direction and that the level of vertical stress significantly affects the horizontal suffusion, such as the initiation and failure hydraulic gradient for suffusion as well as accumulated eroded weight.

458. Molecular SARS-CoV-2 Testing During the COVID-19 Outbreak: Experiences of a Hospital in Southeast Michigan, USA

BackgroundThe novel Coronavirus SARS CoV-2 (COVID-19) outbreak was complicated by the lack of diagnostic testing kits. In early March 2020, leadership at Beaumont Hospital, Royal Oak Michigan (Beaumont) identified the need to develop high capacity testing modalities with appropriate sensitivity and specificity and rapid turnaround time. We describe the molecular diagnostic testing experience since initial rollout on March 16, 2020 at Beaumont, and results of repeat testing during the peak of the COVID-19 pandemic in MI.MethodsBeaumont is an 1100 bed hospital in Southeast MI. In March, testing was initially performed with the EUA Luminex NxTAG CoV Extended Panel until March 28, 2020 when testing was converted to the EUA Cepheid Xpert Xpress SARS-CoV-2 for quicker turnaround times. Each assay was validated with a combination of patient samples and contrived specimens.ResultsDuring the initial week of testing there was > 20 % specimen positivity. As the prevalence grew the positivity rate reached 68% by the end of March (Figure 1). Many state and hospital initiatives were implemented during the outbreak, including social distancing and screening of asymptomatic patients to increase case-finding and prevent transmission. We also adopted a process for clinical review of symptomatic patients who initially tested negative for SARS-CoV-2 by a group of infectious disease physicians (Figure 2). This process was expanded to include other trained clinicians who were redeployed from other departments in the hospital. Repeat testing was performed to allow consideration of discontinuation of isolation precautions. During the surge of community cases from March 16 to April 30, 2020, we identified patients with negative PCR tests who subsequently had repeat testing based on clinical evaluation, with 7.1% (39/551) returning positive for SARS- CoV2. Of the patients who expired due to COVID-19 during this period, 4.3% (9/206) initially tested negative before ultimately testing positive.Figure 1 BH RO testing Epicurve Figure 2: Screening tool for repeat COVID19 testing and precautions ConclusionMany state and hospital initiatives helped us flatten the curve for COVID-19. Our hospital testing experience indicate that repeat testing may be warranted for those patients with clinical features suggestive of COVID-19. We will further analyze these cases and clinical features that prompted repeat testing.Disclosures All Authors: No reported disclosures

Calibrating a profile measurement system for dimensional inspection in rail rolling mills

Modern, high-speed, railway transportation requires rails to conform strictly to requirements specified in various standards. One key requirement is the conformance of the dimensions of the rail cross section to those of the corresponding rail model, within tight tolerances. This paper deals with a system for dimensional quality inspection during the manufacture of railway rails. Optical triangulation is used to build a profile from laser lines projected on the rails from four different locations. Then, the profile is compared to that of the corresponding rail model. The differences between certain numerical values (the dimensions) for the profile and the model are compared to standard tolerances for each dimension in order to detect dimensional defects. As a prerequisite for this, the cameras used to capture the laser lines must be calibrated. Standard calibration plates are unsuitable for sheet-of-light calibration in a production environment, as determining the location of the laser emitters relative to the plates would be an issue. For this reason, a cylinder-based calibration target is used instead. Different calibration algorithms are discussed and compared to said standard calibration. The results of accuracy and repeatability tests in the production environment are also shown. The accuracy of the system is found to be appropriate for the purpose of quality inspection under the requirements of applicable rail standards.

The Feasibility and Repeatability of Ultrasound Microbubble Angiography in the Determination of Pulmonary Blood Volume in Animal Models

To investigate the feasibility of measuring pulmonary blood volume (PBV) by ultrasound microbubble angiography, which may provide a feasible method for further detection of PBV changes. Ultrasound microbubble angiography was used to calculate the PBV by detecting pulmonary transit time (PTT) and heart rate-normalized pulmonary transit time (nPTT). To evaluate the consensus degree based on the intra-, inter-observer and within-day variation in order to determine the repeatability. The method was used for acute left ventricular dysfunction models to determine the feasibility as well. The Bland-Atlman plots showed good intra-observer, within-day, and inter-observer consistency of measurement results. Application in acute left ventricular dysfunction models showed that, compared with the control, left heart failure models had higher PTT, nPTT and PBV ( P<0.05). Detection of PTT/nPTT to calculate PBV by ultrasound microbubble angiography is simple and feasible, it is not easy to produce miscarriage of justice, with good intra- and inter-observer consistency of repeatability test results. The method has certain feasibility.

Anelastic strain recovery in situ stress measurement method and its application prospect in underground mines

Current stress state data are important in underground mine construction, analysis the of tunnel stability, the forecasting of coal and gas rock bursts in underground mines. At present, the hollow inclusion gauge is primarily used for in situ stress measurement in underground mines. However, the sensors of these gauges often fail to fully adhere to the borehole wall, which can reduce the reliability of the measurement results. In this study, the anelastic strain recovery (ASR) in situ stress measurement method based on oriented cores is introduced. The effectiveness of this technique is analyzed by comparing the test results with those obtained by the hydraulic fracturing method. In addition, the reliability of the ASR method is evaluated by repeatability testing. The ASR results indicate a horizontal minimum principal stress error of less than 10% compared with those obtained by the hydraulic fracturing method. The repeatability test results show good consistency in the in situ stress measurement results of two back-to-back test samples. The ASR method is a safe and highly efficient technique that is not limited by the depth and measurement environment. Therefore, it is expected to have broad application for underground mine in situ stress measurement.

Value of 10-2 Visual Field Testing in Glaucoma Patients with Early 24-2 Visual Field Loss

To determine whether the 10-2 test of the Humphrey Field Analyzer detected a higher proportion of abnormal visual fields compared with the 24-2 test in the central 10° of patients with early glaucomatous visual field damage. Prospective observational study. Patients with open-angle glaucoma and healthy control participants. All participants underwent a 24-2 and 10-2 test. Only the 12 central test locations of the 24-2 test were included to analyze equivalent visual field areas. The performance of the 2 tests was compared across 4 pointwise criteria: total deviation (TD) and pattern deviation (PD) analyses at the 5% and 2% levels. Analyses also were conducted for 2 pairs of follow-up tests, each performed 4 months apart. (1) Area under the receiver operating characteristic curve (AUC), (2) sensitivity at identically matched specificity for the 4 criteria, (3) overlap (entire field and by quadrant) of abnormal visual fields with both tests, and (4) repeatability of the findings in 2 subsequent follow-up tests. One eye each of 97 glaucoma patients (median mean deviation, -2.31 dB) and 65 control participants were included in the study. The AUCs for the 24-2 and 10-2 tests were not significantly different for any of the 4 criteria and ranged from 0.88 to 0.93 and from 0.91 to 0.94, respectively. At matched specificity, the sensitivity of the 24-2 test was significantly higher for all criteria except for PD analysis at 5%. In patients with an abnormal field with either test, the overlap varied from 60% to 86% depending on the criterion, whereas by quadrant, concordance ranged from 70% to 87%. Over the follow-up, the repeatability of test results (both 24-2 and 10-2 abnormal, either abnormal, or both normal) was achieved in 55% to 70% of patients. In this study of glaucoma patients with early damage with the 24-2 test, there was little evidence that adding the 10-2 test revealed additional undetected defects in the central visual field. It may be more prudent to reserve 10-2 testing for following up selected patients with higher risk of central visual field progression.

Diagnostic yield of repeat testing for SARS-CoV-2: Experience from a large health system in Los Angeles

ObjectiveTo determine the diagnostic yield of repeat testing for SARS-CoV-2. MethodsA retrospective analysis was performed of all SARS-CoV-2 test results within the UCLA Health System between March 9th and April 29th, 2020. All patients with repeat test results were identified and those with discordant results were reviewed. ResultsBetween March 9th and April 29th there were 10,165 SARS-CoV-2 test results, of which 630 (6.2%) were positive. Among the 904 patients with repeat test results, 808 (89.4%) were initially negative and 96 (10.6%) were initially positive. Among the 808 patients with an initial negative test, 15 (1.9%) subsequently tested positive. Eleven cases with an initial negative SARS-CoV-2 test and without a known prior positive SARS-CoV-2 test were reviewed; 6 were employed as healthcare workers and 10 were positive on the second test. ConclusionsWe found a low diagnostic yield of repeat testing for SARS-CoV-2 in our health system. Repeat testing might prove useful in certain clinical scenarios, such as in healthcare workers, when symptoms develop after a negative test, and in hospitalized patients with a high clinical suspicion for COVID-19.

A new method to determine the heating power of ternary cylindrical lithium ion batteries with highly repeatable thermal runaway test characteristics

A new method to determine the heating power of ternary cylindrical lithium ion batteries with highly repeatable thermal runaway test characteristics is proposed based on statistical principles. By selecting the key parameters for the process of heating-triggered thermal runaway of a lithium ion battery, such as the heating time and thermal runaway temperature, the standard deviation coefficients in multiple tests are used as the basis for evaluating the repeatability and determining the heating power of the highly repeatable thermal runaway test results. A systematic experimental study of four typical ternary cylindrical lithium ion batteries is carried out and a method for calculating the heating power based on the rated energy and weight of the battery is proposed. The results show that this method could effectively ensure the repeatability of the thermal runaway test for cylindrical batteries. The method is simple, original and innovative for the selection of the thermal runaway heating power of ternary cylindrical lithium ion batteries. The results also serve as a reference to select the heating power for other types of lithium ion batteries.

0741 Diagnosing Narcolepsy Type II in the Active Duty Population

Abstract Introduction: Introduction There is a high prevalence of sleep disturbances in U.S. military personnel which can significantly impact continued military service. Narcolepsy is a rare sleep disorder and testing results are often variable, especially when cataplexy is absent. Given the high incidence of confounding sleep disorders in military personnel, including insufficient sleep duration and sleep-disordered breathing, a narcolepsy diagnosis may be even more challenging. As this diagnosis is often incompatible with continued military service, extra attention should be given to confounding diagnoses in military personnel. Methods This is a retrospective study of patients aged 18-65, who were diagnosed with narcolepsy type 1 or type 2 at an outside location and subsequently underwent repeat evaluation at our facility. Polysomnography, actigraphy, and multiple sleep latency test results from the time of the original diagnosis, if available, and repeat evaluation were reviewed. The initial diagnosis was compared to the results of repeat testing and the prevalence of narcolepsy vs. another sleep disorder was assessed. Results Two of twenty-three patients retained a diagnosis of narcolepsy on repeat testing. 10 patients were diagnosed with insufficient sleep syndrome (&amp;lt 7 hours sleep/night), 5 displayed significant circadian misalignment (including irregular sleep/wake periods or delayed sleep phase), and 8 were diagnosed with mild obstructive sleep apnea. 7 of the 8 OSA patients had supine predominate OSA, which may have contributed to not being diagnosed on initial testing. The average total sleep time of the group was 6 hours and 49 minutes, consistent with insufficient sleep duration. Conclusion Narcolepsy type 1 and type 2 are exceedingly rare disorders with diagnostic test results that may be influenced by the presence of other common sleep disorders. In this study, re-evaluation resulted in a changed diagnosis in 91 percent of patients, emphasizing the importance of ruling out these confounding diagnoses. Support

Human Pelvis Bayesian Injury Probability Curves From Whole Body Lateral Impact Experiments.

Injury criteria are used in military, automotive, and aviation environments to advance human safety. While injury risk curves (IRCs) for the human pelvis are published under vertical loading, there is a paucity of analysis that describe IRCs under lateral impact. The objective of the present study is to derive IRCs under this mode. Published data were used from 60 whole-body postmortem human surrogate (PMHS) tests that used repeated testing protocols. In the first analysis, from single impact tests, all injury data points were considered as left censored and noninjury points were considered as right censored, while repeated testing results were treated as interval censored data. In the second analysis, injury data were treated uncensored. Peak force was used as the response variable. Age, total body mass, gender, and body mass index (BMI) were used as covariates in different combinations. Bayesian survival analysis model was used to derive the IRCs. Plus-minus 95% credible intervals (CI) and their normalized CI sizes (NCIS) were obtained. This is the first study to develop IRCs in whole body PMHS tests to describe the human pelvic tolerance under lateral impact using Bayesian models.

Analysis of a New Shape of Test Specimen for Block Shear Impact Test.

This paper reports and discusses an experimental comparison of metal specimens for impact strength research of adhesive connections with different shapes of the upper element. The top element of the specimen of the cuboid shape was replaced with a disc-shaped element. The experimental investigations were supplemented with dynamic numerical calculations of the tested cases. The results of the experimental studies indicate that the material applied to the produce of the top element of the block specimen deformed plastically as a result of applying the load, which further hinders the interpretation of already problematic investigation results. The numerical analysis confirms exceeding the yield point, by stresses, of the material that the specimen elements were made of. Modified specimens were characterized by only little greater repeatability of test results and greater impact strength caused by plastic deformations of the cylindrical specimen element.

SPECT myocardial perfusion imaging in liver transplantation candidates

BackgroundThe optimal cardiovascular evaluation prior to liver transplantation remains controversial and includes stress echocardiography, stress MPI, cardiac CTA, and coronary angiography. This study summarizes our experience of the past decade using SPECT MPI in patients with end-stage liver disease, including patient characteristics, stress testing protocols, test results, the need for repeat testing, and downstream testing. MethodsAll patients who underwent a clinically indicated stress SPECT MPI study as part of their pre-liver transplant evaluation from 2004 to 2014 were reviewed from the Nuclear Cardiology database. Results of perfusion imaging, repeat testing, subsequent angiography, and need for revascularization were reviewed. ResultsA total of 2500 patients were referred for SPECT MPI, of those 111 had known CAD and 271 underwent more than one MPI study. Compared to other patients undergoing stress MPI, pre-liver transplant patients were younger, had fewer cardiac risk factors and lower prevalence of prior cardiac history, and used pharmacologic stress more often. During the study decade, patient age increased, prevalence of hypertension increased and smoking decreased, prevalence of known CAD increased, and the number of abnormal studies decreased. Abnormal perfusion results were present in 7.8% of pre-liver transplant patients compared to 34.3% of all other patients. In a multivariate model, age and lower ejection fraction were associated with an abnormal MPI result. Of the 64 patients who underwent subsequent invasive or non-invasive coronary angiography after an abnormal MPI, obstructive CAD was diagnosed in 25 patients (1.0%), non-obstructive CAD was diagnosed in 23 patients (0.9%), and normal coronaries found in 16 patients (0.6%); a total of 18 (0.7%) of these underwent coronary revascularization. The average time to repeat testing was 27.2 ± 17.9 months. In a multivariate model, younger age and exercise stress were associated with repeat testing. In only 17 patients out of 271 with a normal initial perfusion, the repeat study became abnormal. The use of stress-first imaging was successful in 80% of patients with a reduction in Tc-99m dose from 39.1 to 18.3 mCi. ConclusionAbnormal SPECT MPI results in candidates for liver transplantation are infrequent compared to non-liver transplant patients and the incidence of obstructive CAD on subsequent angiography even less. Repeat testing in those on the transplant waiting list after initial normal test results appears to be of limited value. Stress-first protocols may be considered for the majority of these patients to reduce testing time and radiation exposure.

Determining the Need for Repeat Testing of Blood Ethanol Concentration: Evaluation of the Synchron Blood Ethyl Alcohol Assay Kit.

SummaryBackgroundIn clinical laboratories, a common practice used to verify tests prior to reporting is repeat testing. Our objective was to evaluate the differences between the results of blood ethanol concentration (BEC) test repetitions and report on the role of repeat testing to prevent reporting of incorrect results.MethodsWe conducted a retrospective study of data retrieved from the Bursa Yuksek Ihtisas Training and Research Hospital’s document management system by calculating the percentage change between repeated BEC test runs. To assess for clinical relevance, the bias between two results from the same sample was compared using the 1988 Clinical Laboratory Improvement Amendments’ (CLIA) proficiency testing allowable total error (TEa) limits.ResultsFrom a total of 1,627 BEC tests performed between January 2017 and January 2018, 70% (1,133) were repeat tested. Of these, 830 resulted in BECs between 0–5 mmol/L, of which 237 (28.5%) were above the 25% acceptable TEa. Two hundred seventy-six BEC test results were greater than >14 mmol/L, and there was a good consensus between the initial and repeat test results (99%). In this group, the mean bias was 0.0% (95%, CI = -9.8–9.8%). However, three of the repeat test results were considered significantly different. There were two discordant results in the 5–14 mmol/L ethanol level, and the mean bias was 2.1% (95%, CI = -15.0–19.1%).ConclusionThe majority of the repeated BEC test values were the same as the baseline value; therefore, there may be limited benefit in continuing such frequent repeated analyses.

Effect of solvent lamination on roll-to-roll hot-embossed PMMA microchannels evaluated by optical coherence tomography

Manufacturing of microfluidic based diagnostic devices requires small tolerances and uniform quality to guarantee reliable and repeatable test results. This work describes characterization of morphological changes that occur to a hot embossed PMMA microfluidic channel after solvent lamination with a PMMA lid. A non-contact cross-sectional analysis of the lidded microfluidic device was performed by optical coherence tomography (OCT). The solvent induced morphology change led to a porous structure in bottom corners of hot-embossed channels, which allowed a fluid to absorb in the material. The measurements of solvent diffusion showed faster diffusion rate at the corners of the channel, in which the accumulated stress during the embossing process was the highest. The stress profile was verified by simulation of von Mises stresses during a molding phase of a hot embossing process. The porous structure with increased fluid diffusion has an unwanted effect on bioassay result, e.g. when detection molecules leak into the substrate thus leading to unspecific signal on chip. OCT was found to be a valuable, non-destructive imaging method to monitor solvent diffusion process and lamination process quality.

A Multi-Center Assessment of Thyroid Function Test Precision in Chemiluminescence Immunoassay (CLIA) Systems

Background: Chemiluminiscence immunoassay (CLIA) is exclusively pragmatic technology for the analysis of biomarker for diagnosis of thyroid disorders. However, performance characteristics of different chemiluminescence immunoassay (CLIA) systems supplied by different manufacturers in diverse set up for thyroid function test (TFT) has not yet been studied well.&#x0D; Objective: Our aim is to evaluate laboratory results by assessment of the reproducibility and repeatability of TFTs in three different diagnostic set up to assure the quality of thyroid hormone assay using chemiluminescence immunoassay (CLIA) instruments: Advia Centaur CP (Siemens), Access 2 (Beckman Coulter) and Liaison (Diasorin).&#x0D; Materials and Methods: Among the adult male and female individuals visited for thyroid hormone assay, 51 normal individuals were selected for the study. Three aliquots of serum samples were distributed to assess the reproducibility of three different CLIA equipments operated in three diagnostic centers. Additional three aliquots of serum were analyzed weekly for TFT (fFT3, fFT4 and TSH) to check the repeatability of assay in ADVIA Centaur CP set up. Assay precision was determined by reproducibility and repeatability of test results.&#x0D; Results: Results of TFTs of serum samples obtained from three different interlaboratory assays using different CLIA systems have achieved good precision showing minimal variance (P&gt;0.05) and acceptable reproducibility. Results are also precise with adequate repeatability showing minimal variance (P &gt;0.05) obtained from the three different intra-laboratory assays in a single CLIA system using ADVIA Centaur CP by same team.&#x0D; Conclusion: Our study elucidates the thyroid hormone assay performance of CLIA systems in three centers, which has shown assay precision with good reproducibility and repeatability of thyroid hormone assay. Thus, the analysis of precision as an essential component of quality control is necessary to deliver precise diagnostic services.

Glass fiber load optimization of the preparation and characterization of TiO2 photocatalytic materials

I using the sol-gel/immacing jacquard to load TiO2 film on the fiberglass. Through orthogonal test, the photocatalytic performance of the photocatalytic degradation of nitrobenzene wastewater by the loading TiO2 was investigated, including the ratio of glue solution, the calcination temperature, the calcination time and the number of times of coating. The best condition of preparation of glass fiber load titanium dioxide thin film is: ethanol: water: the molar ratio of nitrate 10:6:1, calcination temperature is 450 °C, calcination time is 90 minutes, coating number 4 times. The repeated test results showed that under the optimal preparation conditions, the degradation rate of nitrobenzene with a concentration of 40mg/L was up to 93.4%. The catalyst can be reused. The results of electron microscopy showed that the catalyst on the surface of glass fiber was evenly distributed in a tubular shape. The XRD resulted show that the crystal type of TiO2 supported by glass fiber is sharp-titanium ore type with good photocatalytic performance.

Errors of Classification With Potassium Blood Testing: The Variability and Repeatability of Critical Clinical Tests

ObjectiveTo understand the performance of a currently used clinical blood test with regard to the frequency and size of variation of the results. Patients and MethodsFrom November 29, 2012, through November 29, 2013, patients were recruited at 65 sites as part of a previously reported clinical trial (ClinicalTrials.gov Identifier: NCT01737697). Eligible outpatients who had been fasting for at least 8 hours underwent venous phlebotomy at baseline, 30 minutes, and 60 minutes to measure plasma potassium levels in whole blood using a point-of-care device (i-STAT, Abbott Laboratories). We analyzed the results to assess their variability and frequency of pseudohyperkalemia and pseudonormokalemia. ResultsA total of 1170 patients were included in this study. Absolute differences between pairs of measurements from different time points ranged from 0 to 2.5 mmol/L, with a mean difference of 0.26 mmol/L. The mean percentage differences were approximately 5% with an SD of 5%. Approximately 12% of differences between repeated fasting potassium blood test results were above 0.5 mmol/L (33% of the normal range), and 20% of patients (234) had at least one difference greater than 0.5 mmol/L. In 44.0% of the patients with a hyperkalemic average value (true hyperkalemia) (302 of 686), at least one blood test result was in the normal range (pseudonormokalemia), and in 30.2% of the patients with a normal average value (146 of 484), at least one blood test result was elevated (pseudohyperkalemia). ConclusionExpected variability and errors exist with potassium blood tests, even when conditions are optimized. Pseudohyperkalemia and pseudonormokalemia are common, indicating a need for thoughtful clinical interpretation of unexpected test results.