False positive urine amphetamine immunoassay due to solriamfetol.

Solriamfetol is a schedule IV-controlled substance used to treat excessive daytime sleepiness resulting from narcolepsy or obstructive sleep apnea. We present a patient prescribed solriamfetol who tested positive for amphetamines on a routine urinary toxicology screen despite patient denial of illicit drug use, raising the possibility of a false positive amphetamine screen. Spiking studies were performed on negative urine, and different concentrations of solriamfetol drug on 2 different amphetamine assays: the commonly used Beckman Emit® II Plus Amphetamines Assay, and the Citrine™ Triple Quad™ MS/MS Systems. The Beckman yielded positive results for amphetamines at solriamfetol concentrations of 200 µg/mL and 2000 µg/mL and negative results at 0.2 µg/mL and 2 µg/mL. However, the Citrine™ Triple Quad™ MS/MS Systems was negative at all concentrations. The Beckman Emit® II Plus Amphetamine Assay gave false positive results for amphetamines due to solriamfetol drug usage, a finding of relevance to prescribers of solriamfetol.

AACC Guidance Document on the Use of Point-of-Care Testing in Fertility and Reproduction.

BACKGROUND: The AACC Academy revised the reproductive testing section of the Laboratory Medicine Practice Guidelines: Evidence-Based Practice for Point-of-Care Testing (POCT) published in 2007. METHODS: A panel of Academy members with expertise in POCT and laboratory medicine was formed to develop guidance for the use of POCT in reproductive health, specifically ovulation, pregnancy, premature rupture of membranes (PROM), and high-risk deliveries. The committee was supplemented with clinicians having Emergency Medicine and Obstetrics/Gynecology training. RESULTS: Key recommendations include the following. First, urine luteinizing hormone (LH) tests are accurate and reliable predictors of ovulation. Studies have shown that the use of ovulation predicting kits may improve the likelihood of conception among healthy fertile women seeking pregnancy. Urinary LH point-of-care testing demonstrates a comparable performance among other ovulation monitoring methods for timing intrauterine insemination and confirming sufficient ovulation induction before oocyte retrieval during in vitro fertilization. Second, pregnancy POCT should be considered in clinical situations where rapid diagnosis of pregnancy is needed for treatment decisions, and laboratory analysis cannot meet the required turnaround time. Third, PROM testing using commercial kits alone is not recommended without clinical signs of rupture of membranes, such as leakage of amniotic fluid from the cervical opening. Finally, fetal scalp lactate is used more than fetal scalp pH for fetal acidosis due to higher success rate and low volume of sample required. CONCLUSIONS: This revision of the AACC Academy POCT guidelines provides recommendations for best practice use of POCT in fertility and reproduction.

Technical Note: Glycolic Acid Exacerbates the Analytical Performance of Lactate Assay.

In this study, we evaluated the analytical interference of glycolic acid on several lactate assays that use lactate oxidase and dehydrogenase. Herein, we tested the effect of different concentrations of glycolic acid (0.01-46mM) on the lactate assay by using central lab and point of care (POCT) analyzers: Radiometer ABL 800, Beckman AU480, Roche Cobas c502, and Abbott i-STAT. Glycolic acid concentrations as low as 0.12mM resulted in a ≥20% positive bias in lactate assay on the ABL 800 and a concentration of approximately 0.23mM resulted in >20% on the Roche Cobas c502 and Abbott i-STAT. A significant lactate gap is found at concentrations >0.06mM between the Radiometer ABL 800 and Roche Cobas c502/Abbott i-STAT. However, at concentrations ≥0.92mM, the lactate gap is very significant among all three platforms. Falsely elevated lactate levels could result in misdiagnosis.

Utilization of Laboratory Testing Algorithms for Celiac Disease in a Pediatric Hospital.

BACKGROUND: At Texas Children's Hospital in Houston, numerous celiac tests are ordered from a wide range of nonspecialty healthcare providers. OBJECTIVE: To retrospectively examine the ordering of celiac tests before and after a test ordering initiative at our institution, to determine whether the initiative impacted appropriate usage of those tests and affected costs. METHODS: We carefully scrutinized all orders for comprehensive celiac testing from July 2016 through September 2017, implemented an in-house celiac-disease screening cascade, and reflexed it to the comprehensive celiac testing panel if an abnormal screening result was obtained. RESULTS: A total of 60 celiac test orders were issued during the 14-month study period. The ordering physician was a gastroenterologist in 6 cases and a nongastroenterologist in 54 cases. Of the 60 orders, only 4 were approved for sending out for comprehensive celiac testing; in 52 of the 60 cases, the order was altered to celiac screening. In the remaining 4 cases, the tests were canceled as a result of incorrect orders. Only 1 of the 52 celiac screenings yielded a positive result and thus was reflexed to the comprehensive panel. CONCLUSIONS: We were able to induce appropriate celiac test usage by implementing a celiac-reflexive cascade. Also, our strategy proved to be extremely cost effective.

Revisiting sweat chloride test results based on recent guidelines for diagnosis of cystic fibrosis.

OBJECTIVES: Recent sweat chloride guidelines published by the Cystic Fibrosis Foundation changed the intermediate sweat chloride concentration range from 40-59 mmol/L to 30-59 mmol/L for age > 6 months. We wanted to know how this new guideline would impact detection of cystic fibrosis among patients who previously had sweat tests done at Texas Children's Hospital. METHODS: We revisited sweat chloride test results (n = 3012) in the last 5 years at Texas Children's Hospital based on the new guidelines on diagnosis of cystic fibrosis from the Cystic Fibrosis Foundation. RESULTS: We identified 125 patients that would be reclassified in the intermediate sweat chloride value with the new guidelines that were classified as "unlikely to have CF" in the previous guidelines. 8 (32%) patients with CFTR gene testing were positive for CFTR gene mutation(s). 4 (50%) of these patients were identified to have 2 CFTR mutations. One had variant combination that was reported to cause CF but all were diagnosed with CFTR-related metabolic syndrome. CONCLUSION: Our findings concur with the new CF diagnosis guidelines that changing the intermediate cut-off to 30-59 mmol/L sweat chloride concentration in combination with CFTR genetic analysis enhances the probability of identifying individuals that have risk of developing CF or have CF and enables for earlier therapeutic intervention.

Accuracy of Two Progesterone Immunoassays for Monitoring In Vitro Fertilization.

BACKGROUND: Progesterone concentrations are routinely monitored during in vitro fertilization cycles. Immunoassay-based platforms are used most often in this setting because they are simple to use and amenable to same-day sample collection and result-reporting. However, immunoassay methods are subject to variation in specificity between different assay manufacturers. In this study, a set of unexpectedly high progesterone concentrations led to a method comparison between two in-house immunoassay platforms relative to the reference method. METHODS: Progesterone was measured in 28 serum samples from women undergoing IVF cycles using the Siemens ADVIA Centaur Immunoassay system and the Abbott Architect i1000SR analyzer. A subset of these samples was selected for progesterone measurement by liquid chromatography-tandem mass spectrometry to define the accuracy of each immunoassay. RESULTS: The Siemens ADVIA Centaur immunoassay system overestimated progesterone concentrations by 19% and the Abbott Architect overestimated progesterone concentrations by 5%. CONCLUSIONS: The Abbott Architect progesterone immunoassay provides a more accurate measurement of serum progesterone than the Centaur immunoassay at concentrations relevant for monitoring in vitro fertilization populations.

Discordant Analytical Results Caused by Biotin Interference on Diagnostic Immunoassays in a Pediatric Hospital.

Recent studies have reported that biotin interferes with certain immunoassays. In this study, we evaluated the analytical interference of biotin on immunoassays that use streptavidin-biotin in our pediatric hospital. We tested the effect of different concentrations of biotin (1.5-200 ng/ml) on TSH, Prolactin, Ferritin, CK-MB, ß-hCG, Troponin I, LH, FSH, Cortisol, Anti-HAV antibody (IgG and IgM), assays on Ortho Clinical Diagnostic Vitros 5600 Analyzer. Biotin (up to 200 ng/mL) did not significantly affect Troponin I and HAV assays. Biotin (up to 12.5 ng/ml) resulted in <10% bias in CK-MB, ß-hCG, AFP, Cortisol, Ferritin assays and biotin >6.25 ng/mL significantly affected TSH (>20% bias) assay. Prolactin was significantly affected even at low levels (Biotin 1.5 ng/mL). Thus, we recommend educating physicians about biotin interference in common immunoassays and adding an electronic disclaimer.

Validation of an Automated Assay for Levetiracetam (Keppra) on Vitros 5600.

OBJECTIVE: Levetiracetam (also known as Keppra™) is an antiepileptic drug that has been demonstrated as an effective adjunctive therapy in the treatment of partial onset of seizures, primary generalized tonic-clonic seizures, and myoclonic seizures. The aim of our study was to validate an automated quantitative immunoassay for levetiracetam at Texas Children's Hospital. METHOD: We validated the analytical performance of ARK™ Levetiracetam Assay on an Ortho Clinical Diagnostic Vitros 5600 Analyzer at Texas Children's Hospital. Analytical performance parameters included precision, linearity, sensitivity, accuracy, and effect of common interferents (free hemoglobin, bilirubin, triglycerides). We also tested common drug interferents on the ARK Levetiracetam Assay. RESULTS: The assay showed good precision with <4% coefficient of variation (%CV) for intraassay and <7% for interassay precision, respectively. The assay was linear across the measurement range (0.0-100.00 µg/mL). No significant effect was seen with common interferents or commonly co-used drugs. CONCLUSIONS: The ARK Levetiracetam Assay on Ortho Clinical Diagnostic Vitros 5600 can be used for routine determination of levetiracetam for conducting therapeutic drug monitoring and optimizing individual dosage regimen.