Tennessee hospital noncompliance with price transparency legislation for 8 common laboratory tests

OBJECTIVES

The goal of this study was to assess hospital compliance with federal price transparency mandates and barriers to pricing information in Tennessee.

METHODS

All hospitals websites were queried for gross, cash, and BlueCross BlueShield of Tennessee prices for 8 high-frequency laboratory tests in 2 Centers for Medicare & Medicaid Services-mandated pricing sources: (1) a machine-readable file of all available services and (2) a consumer-friendly display of 300 shoppable services. Barriers, including click counts, data availability, and intrahospital price discrepancies, were noted.

RESULTS

Of the 145 Tennessee hospitals assessed, 97.2% were noncompliant with the Centers for Medicare & Medicaid Services final rule. Subanalysis of available machine-readable files, price estimators, and shoppable services files demonstrated 49.6%, 95.1%, and 78.6% noncompliance, respectively. Barriers to pricing information included requiring protected health information (55.9%), missing at least 1 pricing source (7.6%), having no pricing sources available (6.2%), and involving more than 3 clicks to access the cash price in machine-readable files (54.1%) and price estimators (68.6%.) Average intrahospital discrepancy for basic metabolic panel cash prices across pricing sources was $101.30 (range, $0-1012.40).

CONCLUSIONS

Our study showed high levels of noncompliance with price transparency laws, inconsistent and inaccessible pricing, and continued challenges facing patients in Tennessee.

Spironolactone metabolite causes falsely increased progesterone in the Abbott Architect immunoassay

BACKGROUND

Immunoassays are important for routine clinical testing and medical diagnosis. However, they are limited by cross-reactivity especially at low analyte concentrations. There is a critical need to investigate compounds that can interfere with immunoassays. Herein, we describe the identification of canrenone, a spironolactone metabolite that falsely increases progesterone concentrations on the Abbott Architect i2000 Immunoassay.

METHODS

Serum samples and assay diluents were spiked with spironolactone or canrenone and progesterone concentrations were measured on the Architect i2000 and Immulite XPi immunoassay platforms. Blood samples from patients taking spironolactone were analyzed with liquid chromatography-tandem mass spectrometry to evaluate the intrinsic response of progesterone concentrations to the presence of canrenone.

RESULTS

We measured approximately 10-fold higher progesterone concentrations on the Abbott Architect i2000 compared to reference immunoassay analyzers (Siemens Immulite XPi and Roche Cobas e601/602), suggesting an analytical error which is unique to the Architect i2000 antibody and/or assay conditions. By measuring serum progesterone after addition of spironolactone or canrenone to serum samples, we found that canrenone falsely increased progesterone on the Architect i2000 immunoassay. However, this interference was more pronounced at low serum progesterone concentrations. Moreover, a strong positive correlation was seen between canrenone and measured serum progesterone concentrations.

CONCLUSIONS

Our investigations are important for individuals who require progesterone measurements using the Architect i2000 immunoassay, especially because it is unlikely for clinicians to order canrenone measurements alongside progesterone measurements for individuals taking spironolactone. Further research is needed to determine whether canrenone can influence progesterone measurements on other immunoassay systems.

College of American Pathologists Quality Cross Check -Chemistry and Therapeutic Drug Monitoring as a tool for biannual instrument correlations

BACKGROUND

Biannual instrument-correlation studies are required for nonwaived assays performed on multiple instruments.

OBJECTIVE

To determine the feasibility of using College of American Pathologists (CAP) Quality Cross Check-Chemistry and Therapeutic Drug Monitoring (CZQ) to assess instrument correlations among multiple analyzers, analyzer models, and Clinical Laboratory Improvement Amendments (CLIA) licenses for 55 unique analytes.

METHODS

Instrument correlation studies were performed on 9 Abbott ARCHITECT instruments (c4000 [n = 4], c8000 [n = 2], and c16000 [n = 3]) over 3 CLIA licenses using CZQ materials. The mean (SD) values, concentration difference, percent bias, and peer data for each individual level of CZQ were determined for each individual analyzer. Acceptable concentration and percentage for each analyte were set using criteria from CAP or other reputable sources such as the American Association of Bioanalysts or the Royal College of Pathologists of Australasia. Peer data were provided by CAP with the CZQ kit.

RESULTS

Correlations using CZQ materials showed that 94.5% of assays studied were within the acceptability criteria by percent bias only and 98.2% were within acceptability criteria by concentration difference.

CONCLUSIONS

The use of CZQ provides support to standardized correlation studies among instruments within and across separate CLIA licenses. However, widespread adoption of CZQ may be limited due to concerns regarding matrix effects, analyte ranges, and ease of data analysis.

Opportunities for recycling in an automated clinical chemistry laboratory produced by the comprehensive metabolic panel

OBJECTIVES

Clinical laboratories perform a variety of tests for which biomedical waste is a byproduct. Of these, the complete metabolic panel (CMP) produces a significant portion of this waste. We investigated specific waste subsequent to performing CMPs over the course of a year and analyzed what percentage of the waste produced could have been recycled.

METHODS

Patient testing volumes were collected retrospectively from July 14, 2021, to July 14, 2022, for individual assays within the CMP performed on Abbott Alinity c instruments (n = 6). The average weights for components of the reagent kits, which includes wedges, boxes, and package inserts, were calculated. These weights, in conjunction with total patient testing volumes, were used to determine the amount of waste produced.

RESULTS

A total of 1089.2 kg of reagent kit waste was estimated to be produced by performing CMPs throughout a year. Of this waste, most (855.5 kg) was not recyclable, but a subset (233.6 kg) was. Overall, 21.4% of the total specific waste weight was found to be recyclable.

CONCLUSIONS

The CMP contributes a substantial amount of waste when performed on chemistry analyzer platforms in the clinical laboratory. Paper inserts and cardboard packaging, however, presented opportunities for recycling.

Cannabis positivity rates in 17 emergency departments across the United States with varying degrees of marijuana legalization

BACKGROUND

Many states in the United States have progressed towards legalization of marijuana including decriminalization, medicinal and/or recreational use. We studied the impact of legalization on cannabis-related emergency department visits in states with varying degrees of legalization.

METHODS

Seventeen healthcare institutions in fifteen states (California, Colorado, Connecticut, Florida, Iowa, Kentucky, Maryland, Massachusetts, Missouri, New Hampshire, Oregon, South Carolina, Tennessee, Texas, Washington) participated. Cannabinoid immunoassay results and cannabis-related International Classification of Diseases (ninth and tenth versions) codes were obtained for emergency department visits over a 3- to 8-year period during various stages of legalization: no state laws, decriminalized, medical approval before dispensaries, medical dispensaries available, recreational approval before dispensaries and recreational dispensaries available. Trends and monthly rates of cannabinoid immunoassay and cannabis-related International Classification of Diseases code positivity were determined during these legalization periods.

RESULTS

For most states, there was a significant increase in both cannabinoid immunoassay and International Classification of Diseases code positivity as legalization progressed; however, positivity rates differed. The availability of dispensaries may impact positivity in states with medical and/or recreational approval. In most states with no laws, there was a significant but smaller increase in cannabinoid immunoassay positivity rates.

CONCLUSIONS

States may experience an increase in cannabis-related emergency department visits with progression toward marijuana legalization. The differences between states, including those in which no impact was seen, are likely multifactorial and include cultural norms, attitudes of local law enforcement, differing patient populations, legalization in surrounding states, availability of dispensaries, various ordering protocols in the emergency department, and the prevalence of non-regulated cannabis products.

The impact of environmental factors on external and internal specimen transport

The environment that a clinical specimen is exposed to is an important preanalytical factor in laboratory testing. There are numerous environmental conditions that a specimen may experience before it arrives at the clinical laboratory for analysis. Specimens collected at offsite locations are typically stored at the site and transported to the clinical laboratory via courier. Depending on the geographic location, season, method of storage and method of transport, the specimen can experience varying climate conditions that can lead to inaccurate test results. Specimens collected within the healthcare institution are not exempt from suboptimal storage and transport environments. For example, specimens transported via pneumatic tube systems can experience extreme agitation and rapid accelerations and decelerations. Suboptimal storage and transport temperatures occur less frequently within health systems due to multiple regulatory requirements for temperature monitoring; however, temperature monitoring may not occur at every stage of the preanalytical phase. This review will highlight both internal and external environmental conditions that can cause preanalytical errors in clinical laboratory testing. Strategies to mitigate environmentally-induced preanalytical errors and regulatory gaps for environmental monitoring in the preanalytical phase will also be discussed.

Temperature Optimization Within 2 Uniquely Designed Courier Lockboxes During Extreme Summer Temperatures

OBJECTIVES

To determine optimal temperature profiles for 2 uniquely designed courier lockboxes (steel vs polymer) by standardizing daily ice (-20ºC) and cold (4-8ºC) pack placement.

METHODS

Paired courier lockboxes were placed outside in direct sunlight. Ambient outdoor and lockbox temperatures were monitored during 2 4-day cycles, and temperature mean and range were determined daily (time frame, 4:00-10:00 pm). Control lockboxes without packs were compared with experimental paired lockboxes with either 2 cold packs placed at 4:00 pm or 4 ice packs placed at 8:00 am and replaced with 4 cold packs at 4:00 pm daily.

RESULTS

Cycle 1 mean temperatures within control steel and polymer lockboxes were 31.8ºC (range, 18.4-44.1ºC) and 37.2ºC (range, 27.1-46.7ºC), respectively. The addition of 2 cold packs at 4:00 pm reduced mean temperatures to 29.1ºC (range, 19.1-37.2ºC) and 25.3ºC (range, 20.0-31.6ºC) in steel and polymer boxes, respectively. Cycle 2 mean temperatures within control steel and polymer lockboxes were 28.3ºC (range, 22.4-40.8ºC) and 31.6ºC (range, 23.8-41.0ºC), respectively. The addition of 4 ice packs at 8:00 am and replacement with 4 cold packs at 4:00 pm reduced mean temperatures to 24.3ºC (range, 17.4-27.9ºC) and 13.4ºC (range, 6.6-18.1ºC) in steel and polymer boxes, respectively.

CONCLUSIONS

Standardizing instructions for ice and cold packs can decrease internal courier lockbox temperatures.

A High-Value Care Curriculum Using Individual and Group Structured Reflection

OBJECTIVE

One-third of all healthcare dollars are wasted, primarily in the form of clinician-ordered unnecessary diagnostic tests and treatments. Medical education has likely played a central role in the creation and perpetuation of this problem. We aimed to create a curriculum for medical students to promote their contribution to high-value care conversations in the clinical environment.

METHODS

At a large university medical center between March 2017 and February 2018, we implemented a 3-phase curriculum combining multimodal educational initiatives with individual and group reflection for third-year medical students during their 12-week long Internal Medicine clerkship rotation. Students were asked to identify examples of clinical decision making that lacked attention to high-value care, propose solutions to the identified situation, and pinpoint barriers to the implementation of effective solutions using a structured reflection framework and then participate in a debrief debate with fellow students. To assess the curriculum, reflective narratives were coded by frequency and codes were compared with one another and with relevant high-value care literature to identify patterns and themes.

RESULTS

In total, 151 medical students participated in phase 1 and 119 in phase 3. For phase 2, 126 reflective narratives (94.7% participation rate) comprised 226 problems, 280 solutions, and 179 barriers.

CONCLUSIONS

When provided appropriate resources, medical students are able to identify relevant examples of low-value care, downstream solutions, and barriers to implementation through a structured reflection curriculum comprising written narratives and in-person debate.

Standardizing Instructions for Ice and Cold Pack Use Can Mitigate Summer Temperatures on Two Commercially Available Outdoor Courier Lockboxes

Introduction/Objective

Clinical and Laboratory Standards Institute document GP44 recommends samples avoid temperatures >22°C during sample transport and storage. Outdoor courier lockboxes used in external sample transport can experience extreme temperatures (>40°C) in the summer. Ice (frozen at -20°C) and cold (refrigerated at 4-8°C) packs can be used to reduce internal lockbox temperatures during hot summer days. Unfortunately, there are no universally accepted instructions to maintain internal lockbox temperatures during these conditions. Therefore, our goal was to elucidate the impact of placing ice and cold packs at two specific time points to mitigate external summer temperatures in two commercially available outdoor courier lockboxes used at our institution.

Methods/Case Report

Two pairs of uniquely manufactured courier lockboxes (steel vs. urethane polymer) were placed outside in direct sunlight in Nashville, Tennessee during the second week of June 2021. Ambient outdoor and lockbox temperatures were monitored using data loggers during a four-day cycle. Each type of lockbox design had a control with no ice or cold packs. These controls were then compared to each experimental, paired lockbox with four ice packs placed at 8am and replaced with four cold packs at 4pm.

Results (if a Case Study enter NA)

The mean ambient outdoor temperature over these four days was 27.7°C (range: 22.2-39.8°C). Temperatures within the steel and urethane polymer lockboxes without ice or cold packs was 28.3°C (range: 22.4-40.8°C) and 31.6°C (range: 23.8-41.0°C), respectively. The addition of four ice packs at 8am and replaced with four cold packs at 4pm reduced temperatures in the steel box to 24.3°C (range: 17.4-27.9°C) whereas in the urethane polymer box temperatures were reduced to 13.4°C (range: 6.6-18.1°C).

Conclusion

Temperatures inside outdoor lockboxes can increase in summer commonly above the outdoor ambient temperature. Standardizing instructions for ice and cold packs can reduce internal outdoor courier lockbox temperatures during summer months, especially in urethane polymer lockboxes.

Outdoor Courier Lockboxes in Summer Are a Significant Source of Preanalytical Error

OBJECTIVES

To determine the impact of short-term (<4-hour) exposure of summer-like temperatures on lithium heparin (uncentrifuged and centrifuged) samples stored in outdoor courier lockboxes in the Mid-Atlantic United States.

METHODS

Healthy adults (n = 8) were recruited to investigate the impact of the short-term exposure of lithium heparin samples (centrifuged and uncentrifuged) inside 2 LabLocker-KF300 courier lockboxes placed outside in direct sunlight during summer. Each courier lockbox was monitored every 5 minutes with a temperature data logger and contained either the standard number (n = 2) of cold packs (cold) or no standard cold packs (warm). Acceptable tolerance limits were defined for each analyte by significant change limit (SCL) analysis (P < .05), as previously described.

RESULTS

Significant changes were identified in each study condition for warm and cold lockbox conditions. Aspartate aminotransferase, glucose, lactate dehydrogenase, and potassium commonly crossed SCLs from mean baseline (t0) in the majority of conditions.

CONCLUSIONS

Outdoor courier lockboxes are an underrecognized source of preanalytical error.

Cross-Institutional Evaluation of the Abbott ARCHITECT SARS-CoV-2 IgG Immunoassay

OBJECTIVE

To describe a cross-institutional approach to verify the Abbott ARCHITECT SARS-CoV-2 antibody assay and to document the kinetics of the serological response.

METHODS

We conducted analytical performance evaluation studies using the Abbott ARCHITECT SARS-CoV-2 antibody assay on 5 Abbott ARCHITECT i2000 automated analyzers at 2 academic medical centers.

RESULTS

Within-run and between-run coefficients of variance (CVs) for the antibody assay did not exceed 5.6% and 8.6%, respectively, for each institution. Quantitative and qualitative results agreed for lithium heparin plasma, EDTA-plasma and serum specimen types. Results for all SARS-CoV-2 IgG-positive and -negative specimens were concordant among analyzers except for 1 specimen at 1 institution. Qualitative and quantitative agreement was observed for specimens exchanged between institutions. All patients had detectable antibodies by day 10 from symptom onset and maintained seropositivity throughout specimen procurement.

CONCLUSIONS

The analytical performance characteristics of the Abbott ARCHITECT SARS-CoV-2 antibody assay within and between 2 academic medical center clinical laboratories were acceptable for widespread clinical-laboratory use.

Quantitative Measurement of IgG to Severe Acute Respiratory Syndrome Coronavirus-2 Proteins Using ImmunoCAP

BACKGROUND

Detailed understanding of the immune response to severe acute respiratory syndrome coronavirus (SARS-CoV)-2, the cause of coronavirus disease 2019 (CO-VID-19) has been hampered by a lack of quantitative antibody assays.

OBJECTIVE

The objective was to develop a quantitative assay for IgG to SARS-CoV-2 proteins that could be implemented in clinical and research laboratories.

METHODS

The biotin-streptavidin technique was used to conjugate SARS-CoV-2 spike receptor-binding domain (RBD) or nucleocapsid protein to the solid phase of the ImmunoCAP. Plasma and serum samples from patients hospitalized with COVID-19 (n = 60) and samples from donors banked before the emergence of COVID-19 (n = 109) were used in the assay. SARS-CoV-2 IgG levels were followed longitudinally in a subset of samples and were related to total IgG and IgG to reference antigens using an ImmunoCAP 250 platform.

RESULTS

At a cutoff of 2.5 μg/mL, the assay demonstrated sensitivity and specificity exceeding 95% for IgG to both SARS-CoV-2 proteins. Among 36 patients evaluated in a post-hospital follow-up clinic, median levels of IgG to spike-RBD and nucleocapsid were 34.7 μg/mL (IQR 18-52) and 24.5 μg/mL (IQR 9-59), respectively. Among 17 patients with longitudinal samples, there was a wide variation in the magnitude of IgG responses, but generally the response to spike-RBD and to nucleocapsid occurred in parallel, with peak levels approaching 100 μg/mL, or 1% of total IgG.

CONCLUSIONS

We have described a quantitative assay to measure IgG to SARS-CoV-2 that could be used in clinical and research laboratories and implemented at scale. The assay can easily be adapted to measure IgG to mutated COVID-19 proteins, has good performance characteristics, and has a readout in standardized units.

Quantitative measurement of IgG to SARS-CoV-2 proteins using ImmunoCAP

Background

Detailed understanding of the immune response to SARS-CoV-2, the cause of coronavirus disease 2019 (COVID-19), has been hampered by a lack of quantitative antibody assays.

Objective

To develop a quantitative assay for IgG to SARS-CoV-2 proteins that could readily be implemented in clinical and research laboratories.

Methods

The biotin-streptavidin technique was used to conjugate SARS-CoV-2 spike receptor-binding-domain (RBD) or nucleocapsid protein to the solid-phase of the ImmunoCAP resin. Plasma and serum samples from patients with COVID-19 (n=51) and samples from donors banked prior to the emergence of COVID-19 (n=109) were used in the assay. SARS-CoV-2 IgG levels were followed longitudinally in a subset of samples and were related to total IgG and IgG to reference antigens using an ImmunoCAP 250 platform.

Results

Performance characteristics demonstrated 100% sensitivity and 99% specificity at a cut-off level of 2.5 µg/mL for both SARS-CoV-2 proteins. Among 36 patients evaluated in a post-hospital follow-up clinic, median levels of IgG to spike-RBD and nucleocapsid were 34.7 µg/mL (IQR 18-52) and 24.5 µg/mL (IQR 9-59), respectively. Among 17 patients with longitudinal samples there was a wide variation in the magnitude of IgG responses, but generally the response to spike-RBD and to nucleocapsid occurred in parallel, with peak levels approaching 100 µg/mL, or 1% of total IgG.

Conclusions

We have described a quantitative assay to measure IgG to SARS-CoV-2 that could be used in clinical and research laboratories and implemented at scale. The assay can easily be adapted to measure IgG to novel antigens, has good performance characteristics and a read-out in standardized units.

Clinical Ordering Practices of the SARS-CoV-2 Antibody Test at a Large Academic Medical Center

Background

The novel severe acute respiratory coronavirus 2 (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19) originated in December 2019 and has now infected almost 5 million people in the United States. In the spring of 2020, private laboratories and some hospitals began antibody testing despite limited evidence-based guidance.

Methods

We conducted a retrospective chart review of patients who received SARS-CoV-2 antibody testing from May 14, 2020, to June 15, 2020, at a large academic medical center, 1 of the first in the United States to provide antibody testing capability to individual clinicians in order to identify clinician-described indications for antibody testing compared with current expert-based guidance from the Infectious Diseases Society of America (IDSA) and the Centers for Disease Control and Prevention (CDC).

Results

Of 444 individual antibody test results, the 2 most commonly described testing indications, apart from public health epidemiology studies (n = 223), were for patients with a now resolved COVID-19-compatible illness (n = 105) with no previous molecular testing and for asymptomatic patients believed to have had a past exposure to a person with COVID-19-compatible illness (n = 60). The rate of positive SARS-CoV-2 antibody testing among those indications consistent with current IDSA and CDC guidance was 17% compared with 5% (P < .0001) among those indications inconsistent with such guidance. Testing inconsistent with current expert-based guidance accounted for almost half of testing costs.

Conclusions

Our findings demonstrate a dissociation between clinician-described indications for testing and expert-based guidance and a significantly different rate of positive testing between these 2 groups. Clinical curiosity and patient preference appear to have played a significant role in testing decisions and substantially contributed to testing costs.

Mitigating biotin interference in two Roche immunoassays by premixing biotinylated capturing molecules with streptavidin coated beads

BACKGROUND

Biotin is an interference in many streptavidin-biotin based immunoassays, causing falsely decreased results with sandwich immunoassays and falsely increased results with competitive immunoassays. It has been discussed that premixing streptavidin coated beads and biotinylated capturing molecules may prevent biotin interference. This study was designed to test whether such modification could mitigate biotin interference in two originally susceptible sandwich immunoassays.

METHODS

Roche C-peptide and human growth hormone (hGH) immunoassays utilize three reagent containers for streptavidin coated beads (M), biotinylated capturing antibody (R1) and ruthenylated antibody (R2). The reagents were modified by premixing reagent M and R1. Following incubation, the beads were placed back in the M-container and R1-supernatant back to R1-container. Patient specimens were selected, spiked with biotin to 1055 ng/mL, and measured by both the original, unmodified reagent and modified reagent on Roche cobas e411 analyzer. The biotin interference dose response curves were also compared using pooled patient specimen spiked with different concentrations of biotin.

RESULTS

For the original reagent, 1055 ng/mL of biotin decreased C- peptide results by 88% and hGH results by 97%. After reagent modification, this interference effect was nearly eliminated for C- peptide but remained about 20% decreased for hGH.

CONCLUSION

Premixing streptavidin beads and biotinylated capturing molecules is an effective approach to mitigate biotin interference for certain immunoassays.

Detection of Nicotine and Nicotine Metabolites in Units of Banked Blood

OBJECTIVES

To determine the concentrations of nicotine and nicotine metabolites in RBC units as a means to estimate the point prevalence of exposure within the healthy donor pool.

METHODS

Segments from 105 RBC units were tested for the presence of nicotine, cotinine, or trans-3'-hydroxycotinine by liquid chromatography-tandem mass spectrometry.

RESULTS

Of the 20 (19%) units that contained detectable concentrations of nicotine, cotinine, or trans-3'-hydroxycotinine, 19 (18.1%) contained concentrations consistent with the use of a nicotine-containing product within 48 hours of specimen collection. One RBC unit contained nicotine concentrations consistent with passive exposure.

CONCLUSIONS

Chemicals from nicotine-containing products are detectable within the US RBC supply. Further investigation is needed to determine the risks of transfusion-associated exposure to nicotine and other tobacco-associated chemicals among vulnerable patient populations such as neonates.

Advances in the Diagnosis and Management of Cystic Fibrosis in the Genomic Era

BACKGROUND

Cystic fibrosis (CF) is a complex autosomal recessive disease that continues to present unique diagnostic challenges. Because CF was first described in 1938, there has been a substantial growth of genetic and phenotypic information about the disorder. During the past few years, as more evidence has become available, a consortium of international experts determined that the 2008 guidelines from the CF Foundation needed to be reviewed and updated.

CONTENT

The goal of this review is to highlight the latest advances in CF multidisciplinary care, together with the recent updates to the 2017 CF Foundation diagnostic guidelines.

SUMMARY

Data from newborn screening programs, patient registries, clinical databases, and functional research have led to a better understanding of the CF transmembrane conductance regulator (CFTR) gene. Recent consensus guidelines have provided recommendations for clinicians and laboratorians to better assist with interpretation of disease status and related CF mutations. The highly recommended Clinical and Functional Translation of CFTR project should be the first resource in the evaluation of disease severity for CF mutations. Screen-positive newborns and patients with high clinical suspicion for CF are always recommended to undergo confirmatory sweat chloride testing with interpretations based on updated reference intervals. Every patient diagnosed with CF should receive genotyping, as novel molecular therapies are becoming standard of practice. The future of CF management must consider healthcare system disparities as CF transitions from a historically childhood disease to a predominantly adult epidemic.

Rapid Assessment of Drugs of Abuse

Laboratory testing for drugs of abuse has become standard practice in many settings both forensic and clinical. Urine is the predominant specimen, but other specimens are possible including hair, nails, sweat, and oral fluid. Point-of-care test kits provide for rapid analysis at the site where specimens are collected allowing for immediate action on the results. POCT is based on immunochromatography where the drug in the patient's sample competes with drug and antibody conjugates in the test to develop or block the development of a colored line. Most POCTs are visually interpreted in a few minutes. The potential for false positives is possible due to drug cross-reactivity with the antibodies in the test. False negatives are also possible due to dilution of the sample and the potential for adulteration or sample substitution by the patient. POCT shows more variability than central laboratory testing because of the variety of operators involved in the testing process, but POCT has good agreement for most tests with mass spectrometry provided comparable cutoffs and cross-reactivity of drugs/metabolites are considered. Validation of the test performance with the intended operators will identify potential interferences and operational issues before implementing the test in routine practice. POCT offers faster turnaround of test results provided the limitations and challenges of the test are considered.

The Dual Regulatory Role of Amino Acids Leu480 and Gln481 of Prothrombin

Prothrombin (FII) is activated to α-thrombin (IIa) by prothrombinase. Prothrombinase is composed of a catalytic subunit, factor Xa (fXa), and a regulatory subunit, factor Va (fVa), assembled on a membrane surface in the presence of divalent metal ions. We constructed, expressed, and purified several mutated recombinant FII (rFII) molecules within the previously determined fVa-dependent binding site for fXa (amino acid region 473-487 of FII). rFII molecules bearing overlapping deletions within this significant region first established the minimal stretch of amino acids required for the fVa-dependent recognition exosite for fXa in prothrombinase within the amino acid sequence Ser(478)-Val(479)-Leu(480)-Gln(481)-Val(482). Single, double, and triple point mutations within this stretch of rFII allowed for the identification of Leu(480) and Gln(481) as the two essential amino acids responsible for the enhanced activation of FII by prothrombinase. Unanticipated results demonstrated that although recombinant wild type α-thrombin and rIIa(S478A) were able to induce clotting and activate factor V and factor VIII with rates similar to the plasma-derived molecule, rIIa(SLQ→AAA) with mutations S478A/L480A/Q481A was deficient in clotting activity and unable to efficiently activate the pro-cofactors. This molecule was also impaired in protein C activation. Similar results were obtained with rIIa(ΔSLQ) (where rIIa(ΔSLQ) is recombinant human α-thrombin with amino acids Ser(478)/Leu(480)/Gln(481) deleted). These data provide new evidence demonstrating that amino acid sequence Leu(480)-Gln(481): 1) is crucial for proper recognition of the fVa-dependent site(s) for fXa within prothrombinase on FII, required for efficient initial cleavage of FII at Arg(320); and 2) is compulsory for appropriate tethering of fV, fVIII, and protein C required for their timely activation by IIa.

Amino acid region 1000-1008 of factor V is a dynamic regulator for the emergence of procoagulant activity

Single chain factor V (fV) circulates as an M_r 330,000 quiescent pro-cofactor. Removal of the B domain and generation of factor Va (fVa) are vital for procoagulant activity. We investigated the role of the basic amino acid region 1000–1008 within the B domain of fV by constructing a recombinant mutant fV molecule with all activation cleavage sites (Arg⁷⁰⁹/Arg¹⁰¹⁸/Arg¹⁵⁴⁵) mutated to glutamine (fV^Q3), a mutant fV molecule with region 1000–1008 deleted (fV^ΔB9), and a mutant fV molecule containing the same deletion with activation cleavage sites changed to glutamine (fV^ΔB9/Q3). The recombinant molecules along with wild type fV (fV^WT) were transiently expressed in COS-7L cells, purified, and assessed for their ability to bind factor Xa (fXa) prior to and following incubation with thrombin. The data showed that fV^Q3 was severely impaired in its interaction with fXa before and after incubation with thrombin. In contrast, K_D(app) values for fV^ΔB9 (0.9 nm), fVa^ΔB9 (0.4 nm), and fV^ΔB9/Q3 (0.7 nm) were similar to the affinity of fVa^WT for fXa (0.3 nm). Two-stage clotting assays revealed that although fV^Q3 was deficient in its clotting activity, fV^ΔB9/Q3 had clotting activity comparable with fVa^WT. The k_cat value of prothrombinase assembled with fV^ΔB9/Q3 was minimally affected, whereas the K_m value of the reaction was increased 57-fold compared with the K_m value obtained with prothrombinase assembled with fVa^WT. These findings strongly suggest that amino acid region 1000–1008 of fV is a regulatory sequence protecting the organisms from spontaneous binding to fXa and unnecessary prothrombinase complex formation, which in turn results in catastrophic physiological consequences.