Roy W.A. Peake

Cotinine in Children Admitted for Asthma and Readmission

OBJECTIVE: To explore the relationship between tobacco smoke exposure (reported versus biomarker) and rates of readmission for children hospitalized for asthma. METHODS: We enrolled a prospective cohort of 774 children aged 1 to 16 years admitted for asthma or bronchodilator-responsive wheezing. The primary outcome was at least 1 asthma- or wheeze-related readmission within 1 year. Caregivers reported any tobacco exposure at home, in a secondary residence, or in the car. We measured serum and saliva cotinine levels with mass spectrometry. We used logistic regression to evaluate associations between tobacco exposure and readmissions. RESULTS: A total of 619 children had complete tobacco exposure data; 57% were African American and 76% had Medicaid. Seventeen percent of children were readmitted within 1 year. Tobacco exposure rates were 35.1%, 56.1%, and 79.6% by report, serum, and saliva measures, respectively. Caregiver report of any tobacco exposure was not associated with readmission (adjusted odds ratio: 1.18; 95% confidence interval: 0.79–1.89), but having detectable serum or salivary cotinine was associated with increased odds of readmission (adjusted odds ratio [95% confidence interval]: 1.59 [1.02–2.48] and 2.35 [1.22–4.55], respectively). Among children whose caregivers reported no tobacco exposure, 39.1% had detectable serum cotinine and 69.9% had detectable salivary cotinine. Of the children with reported exposure, 87.6% had detectable serum cotinine and 97.7% had detectable salivary cotinine. CONCLUSIONS: Detectable serum and salivary cotinine levels were common among children admitted for asthma and were associated with readmission, whereas caregiver report of tobacco exposure was not.

A Phase 1, Dose-escalation, Double-blind, Block-randomized, Controlled Trial of Safety and Efficacy of Neosaxitoxin Alone and in Combination with 0.2% Bupivacaine, with and without Epinephrine, for Cutaneous Anesthesia.

Background:Neosaxitoxin (NeoSTX) is a site-1 sodium channel blocker that produces prolonged local anesthesia in animals and humans. Under a Food and Drug Administration–approved phase 1 Investigational New Drug trial, the authors evaluated safety and efficacy of NeoSTX alone and combined with 0.2% bupivacaine (Bup) with and without epinephrine. Methods:The authors conducted a double-blind, randomized, controlled trial involving healthy male volunteers aged 18 to 35 yr receiving two 10-ml subcutaneous injections. Control sites received Bup. In part 1, active sites received (1) 5 to 40 &mgr;g NeoSTX+Saline (NeoSTX-Saline), (2) 5 to 40 &mgr;g NeoSTX+Bup (NeoSTX-Bup), or (3) placebo (Saline). In part 2, active sites received 10 or 30 &mgr;g NeoSTX+Bup+Epinephrine (NeoSTX-Bup-Epi) or placebo. Primary outcome measures were safety and adverse events associated with NeoSTX. Secondary outcomes included clinical biochemistry, NeoSTX pharmacokinetics, and cutaneous hypoesthesia. Results:A total of 84 subjects were randomized and completed the two-part trial with no serious adverse events or clinically significant physiologic impairments. Perioral numbness and tingling increased with NeoSTX dose for NeoSTX-Saline and NeoSTX-Bup. All symptoms resolved without intervention. NeoSTX-Bup-Epi dramatically reduced symptoms compared with other NeoSTX combinations (tingling: 0 vs. 70%, P = 0.004; numbness: 0 vs. 60%, P = 0.013) at the same dose. Mean peak plasma NeoSTX concentration for NeoSTX-Bup-Epi was reduced at least two-fold compared with NeoSTX-Saline and NeoSTX-Bup (67 ± 14, 134 ± 63, and 164 ± 81 pg/ml, respectively; P = 0.016). NeoSTX-Bup showed prolonged cutaneous block duration compared with Bup, NeoSTX-Saline, or placebo, at all doses. Median time to near-complete recovery for 10 &mgr;g NeoSTX-Bup-Epi was almost five-fold longer compared with Bup (50 vs. 10 h, P = 0.007). Conclusion:NeoSTX combinations have a tolerable side effect profile and appear promising for prolonged local anesthesia.

Newborn Screening for Lysosomal Storage Disorders.

Newborn screening is one of the most important public health initiatives to date, focusing on the identification of presymptomatic newborn infants with treatable conditions to reduce morbidity and mortality. The number of screening conditions continues to expand due to advances in screening technologies and the development of novel therapies. Consequently, some of the lysosomal storage disorders are now considered as candidates for newborn screening, although many challenges including identification of late-onset phenotypes remain. This review provides a critical appraisal of the current state of newborn screening for lysosomal storage disorders.

Multicenter evaluation of the thermo scientific prelude for measurement of immunosuppressant drugs using sample preparation liquid chromatography-tandem mass spectrometry.

Abstract: Immunosuppressant drugs (ISDs) are commonly prescribed to solid organ transplant patients. Their narrow therapeutic index and potential for toxicity necessitates careful monitoring of blood concentrations. Liquid chromatography–tandem mass spectrometry (LC-MS/MS) methods are increasingly used for ISD measurement. However, there remain many challenges with this methodology, particularly regarding interassay variability. The Thermo Scientific Prelude is an online extraction/liquid chromatography platform that uses turbulent flow technology coupled with MS/MS. A multicenter evaluation of the Prelude for the measurement of cyclosporine A, tacrolimus, and sirolimus is described. ISDs were measured at each site using standardized protocols. Sample preparation liquid chromatography–MS/MS was performed using the Prelude coupled to a TSQ Vantage. Chromatography was achieved with a Cyclone-P TurboFlow/Accucore C8 column combination using a multisolvent loading and eluting pump system. Mass spectrometry acquisitions were performed in selective reaction monitoring mode and data processed using TraceFinder (version 3.1). Multisite mean imprecision for cyclosporine A ranged from 8.8% (54 mcg/L) to 9.8% (450 mcg/L); for tacrolimus, 4.7% (15.5 mcg/L) to 12.6% (2.5 mcg/L); for sirolimus, 7.4% (19.9 mcg/L) to 16.5% (2.6 mcg/L). Approximately 110 specimens were used for method comparison. For cyclosporine A, mean bias against the multisite mean ranged from −18% to 1%; for tacrolimus, values ranged from −7% to 4%; for sirolimus, values ranged from −4% to 2%. Comparisons of multisite mean Prelude results with routine ISD method results was also performed for cyclosporine A (slope = 0.7878, intercept = 24.16, r = 0.98), tacrolimus (slope = 0.9391, intercept = 0.1017, r = 98), and sirolimus (slope = 0.9618, intercept = 0.1483, r = 0.97). The Prelude ISD method offers acceptable and comparable multisite performance. This study has also highlighted the importance of adopting standardized protocols and LC-MS/MS methods for better comparability between ISD assays.

Family Hardships and Serum Cotinine in Children With Asthma

BACKGROUND AND OBJECTIVE: A better understanding of how poverty-related hardships affect child health could highlight remediable intervention targets. Tobacco smoke exposure may be 1 such consequence of family hardship. Our objective was to explore the relationship between family hardships and tobacco exposure, as measured by serum cotinine, a tobacco metabolite, among children hospitalized for asthma. METHODS: We prospectively enrolled a cohort of 774 children, aged 1 to 16 years, admitted for asthma or bronchodilator-responsive wheezing. The primary outcome was detectable serum cotinine. We assessed family hardships, including 11 financial and social variables, through a survey of the child’s caregiver. We used logistic regression to evaluate associations between family hardship and detectable cotinine. RESULTS: We had complete study data for 675 children; 57% were African American, and 74% were enrolled in Medicaid. In total, 56% of children had detectable cotinine. More than 80% of families reported ≥1 hardship, and 41% reported ≥4 hardships. Greater numbers of hardships were associated with greater odds of having detectable cotinine. Compared with children in families with no hardships, those in families with ≥4 hardships had 3.7-fold (95% confidence interval, 2.0–7.0) greater odds of having detectable serum cotinine in adjusted analyses. Lower parental income and educational attainment were also independently associated with detectable serum cotinine. CONCLUSIONS: Family hardships are prevalent and associated with detectable serum cotinine level among children with asthma. Family hardships and tobacco smoke exposure may be possible targets for interventions to reduce health disparities.

Improved separation and analysis of plasma amino acids by modification of the MassTrak™ AAA Solution Ultraperformance® liquid chromatography method.

BACKGROUND Ultraperformance® Liquid Chromatography (UPLC) is increasingly used for quantitative amino acid screening. The Waters MassTrak™ UPLC Amino Acid Analysis (AAA) Solution kit offers rapid analysis with minimal sample preparation. We describe a simple modification of this method enabling enhanced chromatographic separation of previously problematic analytes with improvements in quantification. METHODS The commercial UPLC method was compared with our modified version of the same method. The modification incorporates eluent buffer of increased organic content run at reduced column temperature. UPLC methods were compared by analyzing amino acids from 57 plasma samples. A comparison (n=131) between the modified UPLC method and ion-exchange chromatography was also carried out. RESULTS The commercial method produced a large negative bias for Tyrosine (-22.72%±14.10) and ornithine (-15.02%±10.07). Assay imprecision of Tyrosine using the commercial method (mean Tyrosine: 72.58 and 31.17μmol/l) produced values of 10.86% and 21.12% respectively, compared with the modified method (3.39% and 4.47%). The comparison of modified UPLC and ion-exchange methods was favorable, validating the improvements observed in amino acid quantification. CONCLUSION The modified UPLC method has eliminated significant bias associated with the commercially available method. The modification is simple, robust and readily adaptable to the current MassTrak™ AAA Solution kit for clinical applications.

Mice With Hepatocyte-Specific Deficiency of Type 3 Deiodinase Have Intact Liver Regeneration and Accelerated Recovery From Nonthyroidal Illness After Toxin-Induced Hepatonecrosis

Type 3 deiodinase (D3), the physiologic inactivator of thyroid hormones, is induced during tissue injury and regeneration. This has led to the hypotheses that D3 impacts injury tolerance by reducing local T3 signaling and contributes to the fall in serum triiodothyronine (T3) observed in up to 75% of sick patients (termed the low T3 syndrome). Here we show that a novel mutant mouse with hepatocyte-specific D3 deficiency has normal local responses to toxin-induced hepatonecrosis, including normal degrees of tissue necrosis and intact regeneration, but accelerated systemic recovery from illness-induced hypothyroxinemia and hypotriiodothyroninemia, demonstrating that peripheral D3 expression is a key modulator of the low T3 syndrome.

Measurement of neosaxitoxin in human plasma using liquid–chromatography tandem mass spectrometry: Proof of concept for a pharmacokinetic application

Neosaxitoxin, a member of the saxitoxin family of paralytic shellfish poisoning toxins, has shown potential as an effective, long-acting, anesthetic. We describe the development and validation of a highly sensitive method for measurement of neosaxitoxin in human plasma using liquid chromatography tandem mass spectrometry (LC-MS/MS) and provide evidence for its use in a human pharmacokinetic study. Samples were prepared using cation exchange solid phase extraction followed by hydrophilic interaction liquid chromatography and MS/MS detection in positive electrospray ionization mode. Multiple reaction monitoring was used to monitor neosaxitoxin (m/z 316.17>220.07) and the internal standard analogue decarbamoylneosaxitoxin (m/z 273.12>180.00). The method was validated for lower limit of quantification, precision, accuracy, linearity and matrix effect. The stability of neosaxitoxin in plasma matrix at various storage conditions was also investigated. Standard curves for calibration were linear (r>0.995) across the assay calibration range, 10 to 1000pg/mL. The analytical measurable range of the assay was 10-10,000pg/mL in plasma matrix. This method has demonstrated excellent sensitivity demonstrating a lower limit of quantification in human plasma of 10pg/mL. The mean, inter-batch variation was <5.2% across the concentration range 30 to 800pg/mL. This method was successfully used in a phase 1 trial to investigate the pharmacokinetic profile of neosaxitoxin in humans following the intravenous administration of the drug at a range of doses up to 40μg. We conclude that our high-sensitivity method for measurement of neosaxitoxin in human plasma is capable of supporting future clinical trials.

Now You See It, Now You Don't: Unidentified Plasma Amino Acid Peak.

A 6-year-old girl in the intensive care unit was being treated for excessive bleeding secondary to coagulopathy. She was given parenteral nutrition and followed up by measurement of plasma amino acids. The amino acid method used precolumn derivatization and ultraperformance liquid chromatography (MassTrak™) with UV detection (Waters Corp.). The resulting chromatogram revealed …

Hyperammonemia in a Child Presenting with Growth Delay, Short Stature, and Diarrhea

A 5-year-old male child was referred to the metabolism clinic with a history of failure to thrive, chronic intermittent emesis, diarrhea, seizures, hypotonia, and growth hormone deficiency. He was also noted to experience frequent falling episodes. Routine biochemistry testing revealed increased plasma ammonia concentration at 184 μmol/L (reference interval, 16–47) and lactate dehydrogenase concentration at 445 U/L (reference interval, 110–295). Plasma free and total carnitine concentrations were decreased at 5 μmol/L (reference interval, 26–60) and 17.1 μmol/L (reference interval, 32–84), respectively. Orotic acid excretion in urine was also markedly increased at >80 mmol/mol creatinine (reference interval, 0.2–1.5). Plasma insulin-like growth factor-I (IGF-I)4 concentration was also decreased at <25 ng/mL (reference interval, 50–286). Paired plasma and urine specimens were collected for amino acid analysis using ultraperformance liquid chromatography. The results are shown in Table 1. View this table: Table 1. Amino acid analysis of paired plasma and urine. This patient has lysinuric protein intolerance (LPI), an autosomal recessive disorder of amino acid transport, caused by mutations in the solute carrier family 7, member 7 ( SLC7A7 ) gene (1, 2, 3). Although the worldwide incidence is not known, LPI is estimated to occur in approximately 1 in 60000 newborns in Finland and Japan (2). The SLC7A7 gene product is the …