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The measurement of free thyroxine (FT4) and free triiodothyronine (FT3) using hybrid quadrupole linear ion trap system
1176
Abstracts
Objective: Comparability testing of the same analytes across laboratory platforms may be assessed in various ways (e.g., Clinical Laboratory Standards Institute/CLSI;C54-1 guideline, CVi-within subject biological variation). Our aim in the present study was to determine the difference in analyte concentrations between the same core chemistry analyzers at 1-laboratory site (i.e., lab-defined); and then prospectively evaluate these criteria at other hospital sites. Methods: Over 22 days, 4 heparin plasma samples randomly selected for a pool (daily); was measured for 20 analytes on 2 Roche P-modular platforms within 1-laboratory. During this timeframe, external proficiency testing was acceptable for these analytes (2 surveys). The 3SD of the observed %difference in concentrations of the analytes between platforms was then calculated. Prospectively, over 5-months, 10 different pooled samples were then assessed at 3-laboratories/2 P-modulars each, for these analytes with the % difference assessed by the 3 criteria (lab-defined, CLSI, CVi). Results: Of the 20 analytes, the lab-defined acceptable difference was higher than either CLSI or CVi criteria for urea(14% vs.13%,12%); AST(21% vs.13%,12%), ALT(27% vs.17%,24%), GGT(18% vs.13%,14%) and was lower for potassium (3% vs.4%,5%), totalC02(17% vs.22%,N/A), and P04(6% vs.9%,9%). Prospectively, for the 10 samples, only Mg (all 3sites, 1sample) and Glucose (1-site, 1sample) resulted in %differences exceeding all 3 criteria. For Mg, the concentration was extremely low (average = 0.15 mmol/L), however, the discordant glucose repeat concentration was not (6.3 vs.5.9 mmol/L). Conclusions: The laboratory-defined criteria appear to have appropriately flagged discordant repeat results. Additional specimens (>4 for pool) may avoid extremely low concentrations, where imprecision of the assays may exceed the allowable % difference. doi:10.1016/j.clinbiochem.2011.06.042
P533 The measurement of free thyroxine (FT4) and free triiodothyronine (FT3) using hybrid quadrupole linear ion trap system R. Huang, H.F. Liu AB SCIEX, 353 Hatch Dr., Foster City, California 94404, USA Objective: Triiodothyronine (T3) and Thyroxine (T4) are tyrosinebased thyroid hormones produced by the thyroid gland and are primarily responsible for the regulation of metabolism. More than 99% of T3 and T4 carried in blood are bound to transport proteins. The remaining is free and biologically active. The major challenges of thyroid analysis are the sensitivity and selectivity method for low level free fractions. Method: A reverse phase LC-MS-MS method was developed using a hybrid quadrupole linear ion trap system for the quantitative analysis of FT 3 and FT4 in both the ESI negative mode and positive mode employing Multiple Reaction Monitoring (MRM). Results: The intensities of T3 and T4 are two times higher in ESI positive mode than in negative mode. However, due to the relatively high noise/background in ESI positive mode, the sensitivities of FT4 and FT3 in ESI negative are comparable to ESI positive mode. Base on these method development results, the sensitivities of FT3 and FT4 in ultra filtration matrix were evaluated. The LC/MS/MS procedure involves an online extraction/cleaning of 50 μL filtration samples followed by an activation of a switching valve for subsequent sample introduction into the mass spectrometer. The LLOQ of FT4 and FT3 in ultrafiltration samples are ~ 2.44 pg/mL and ~ 3.17 pg/mL, respectively. The %RSD for the ultra filtration matrix samples for FT4 is 0.5%– 5.6% and for FT3 is 0.7%–6.5%. Conclusion: An LC/MS/MS analytical method was developed for low level free T3 and T4 detection. doi:10.1016/j.clinbiochem.2011.06.044
P532 An LC-MS/MS analytical method for barbiturate analysis in urine T. Lee, J. McFarlane AB SCIEX, Foster City, CA, USA Objectives: Barbiturates abuse is still a problem even though it has decreased over the years and been replaced by other sedative-hypnotic drugs such as benzodiazepines. Barbiturates cause mild sedation to total anesthesia. Excessive and prolonged use of barbiturate drugs can produce memory loss, irritability, even death. This poster will highlight an analytical method for the quantitation of barbiturates in urine. Methods: The method development process evaluated different sample preparation procedures, calibration curve construction, column selection, mobile phase selection, and ion suppression. Minimal sample preparation is required; a simple dilute-and-shoot for urine samples. Analysis was performed on an AB SCIEX 3200 QTRAP® LC-MS/MS system with a Phenomenex Kinetex C18 50 × 2.1 mm, 2.6 μ column with a flow rate of 700μL/min. Mobile phase A consisted of water with 0.01% Acetic Acid and ammonium formate and mobile phase B consisted of acetonitrile, 0.01% Acetic acid and ammonium formate. Injection volume was 25μL and the total run time was 3.5 minutes. The mass spectrometer was operated in multiple reaction monitoring mode (MRM) in negative ion mode. Each sample was injected in triplicate. Results: The assay was shown to be accurate and precise with %CV and % accuracy within ±15% of nominal across the full linear range (0.1 to 100 ng/mL). Conclusion: A fast, robust, and reliable method for the detection of barbiturates was developed. A simple dilute and shoot procedure was used for sample preparation. Limit of Quantitation (LOQ) for barbiturates were found to be around 0.1 ng/mL. doi:10.1016/j.clinbiochem.2011.06.043
P534 Root cause analysis of delays to discharge for patients held for serial cardiac troponin levels J.J. Owen, A. Worster, B.M. Waines, J. Ward, P. Kavsak, S. Hill Hamilton Health Sciences and McMaster University, Hamilton, ON, Canada Objective: Emergency department (ED) patients with suspected cardiac ischemia often remain in monitor beds for repeat cardiac troponin (cTn) levels to rule out non-ST-elevation myocardial infarction. We sought to identify root causes of delays to ED discharge. Methods: Two blinded data extractors reviewed the process event times of a random sample of ED patients discharged following a second cTn measurement during a one-year period. Process event times included time of ordering of second cTn, time of blood collection, time blood received in lab, time cTn results available, and time of ED discharge. Results: The analyses included 227 randomly selected cases from a total 9656 eligible patients. Mean time from ordering to time of ED discharge was 104.7 min (95% CI 95.3 to 114.0 min). Mean time for blood collection was 4.6 min (95% CI 8.9 to 0.4 min), mean transport time to lab was 15.0 min (95% CI 12.5 to 17.5 min), mean laboratory time was 49.1 min (95% CI 46.8 to 51.5 min), and mean time from results available to patient discharge was 45.2 min (95% CI 36.6 to 53.7). Conclusions: For ED patients held for second cTn levels, blood collection, transport, and laboratory processing times did not appear to be significant causes of delay. From time result available to time of ED discharge represents the largest modifiable time period on which to focus to minimize time patients remain in ED. doi:10.1016/j.clinbiochem.2011.06.045
Abstracts
Objective: Comparability testing of the same analytes across laboratory platforms may be assessed in various ways (e.g., Clinical Laboratory Standards Institute/CLSI;C54-1 guideline, CVi-within subject biological variation). Our aim in the present study was to determine the difference in analyte concentrations between the same core chemistry analyzers at 1-laboratory site (i.e., lab-defined); and then prospectively evaluate these criteria at other hospital sites. Methods: Over 22 days, 4 heparin plasma samples randomly selected for a pool (daily); was measured for 20 analytes on 2 Roche P-modular platforms within 1-laboratory. During this timeframe, external proficiency testing was acceptable for these analytes (2 surveys). The 3SD of the observed %difference in concentrations of the analytes between platforms was then calculated. Prospectively, over 5-months, 10 different pooled samples were then assessed at 3-laboratories/2 P-modulars each, for these analytes with the % difference assessed by the 3 criteria (lab-defined, CLSI, CVi). Results: Of the 20 analytes, the lab-defined acceptable difference was higher than either CLSI or CVi criteria for urea(14% vs.13%,12%); AST(21% vs.13%,12%), ALT(27% vs.17%,24%), GGT(18% vs.13%,14%) and was lower for potassium (3% vs.4%,5%), totalC02(17% vs.22%,N/A), and P04(6% vs.9%,9%). Prospectively, for the 10 samples, only Mg (all 3sites, 1sample) and Glucose (1-site, 1sample) resulted in %differences exceeding all 3 criteria. For Mg, the concentration was extremely low (average = 0.15 mmol/L), however, the discordant glucose repeat concentration was not (6.3 vs.5.9 mmol/L). Conclusions: The laboratory-defined criteria appear to have appropriately flagged discordant repeat results. Additional specimens (>4 for pool) may avoid extremely low concentrations, where imprecision of the assays may exceed the allowable % difference. doi:10.1016/j.clinbiochem.2011.06.042
P533 The measurement of free thyroxine (FT4) and free triiodothyronine (FT3) using hybrid quadrupole linear ion trap system R. Huang, H.F. Liu AB SCIEX, 353 Hatch Dr., Foster City, California 94404, USA Objective: Triiodothyronine (T3) and Thyroxine (T4) are tyrosinebased thyroid hormones produced by the thyroid gland and are primarily responsible for the regulation of metabolism. More than 99% of T3 and T4 carried in blood are bound to transport proteins. The remaining is free and biologically active. The major challenges of thyroid analysis are the sensitivity and selectivity method for low level free fractions. Method: A reverse phase LC-MS-MS method was developed using a hybrid quadrupole linear ion trap system for the quantitative analysis of FT 3 and FT4 in both the ESI negative mode and positive mode employing Multiple Reaction Monitoring (MRM). Results: The intensities of T3 and T4 are two times higher in ESI positive mode than in negative mode. However, due to the relatively high noise/background in ESI positive mode, the sensitivities of FT4 and FT3 in ESI negative are comparable to ESI positive mode. Base on these method development results, the sensitivities of FT3 and FT4 in ultra filtration matrix were evaluated. The LC/MS/MS procedure involves an online extraction/cleaning of 50 μL filtration samples followed by an activation of a switching valve for subsequent sample introduction into the mass spectrometer. The LLOQ of FT4 and FT3 in ultrafiltration samples are ~ 2.44 pg/mL and ~ 3.17 pg/mL, respectively. The %RSD for the ultra filtration matrix samples for FT4 is 0.5%– 5.6% and for FT3 is 0.7%–6.5%. Conclusion: An LC/MS/MS analytical method was developed for low level free T3 and T4 detection. doi:10.1016/j.clinbiochem.2011.06.044
P532 An LC-MS/MS analytical method for barbiturate analysis in urine T. Lee, J. McFarlane AB SCIEX, Foster City, CA, USA Objectives: Barbiturates abuse is still a problem even though it has decreased over the years and been replaced by other sedative-hypnotic drugs such as benzodiazepines. Barbiturates cause mild sedation to total anesthesia. Excessive and prolonged use of barbiturate drugs can produce memory loss, irritability, even death. This poster will highlight an analytical method for the quantitation of barbiturates in urine. Methods: The method development process evaluated different sample preparation procedures, calibration curve construction, column selection, mobile phase selection, and ion suppression. Minimal sample preparation is required; a simple dilute-and-shoot for urine samples. Analysis was performed on an AB SCIEX 3200 QTRAP® LC-MS/MS system with a Phenomenex Kinetex C18 50 × 2.1 mm, 2.6 μ column with a flow rate of 700μL/min. Mobile phase A consisted of water with 0.01% Acetic Acid and ammonium formate and mobile phase B consisted of acetonitrile, 0.01% Acetic acid and ammonium formate. Injection volume was 25μL and the total run time was 3.5 minutes. The mass spectrometer was operated in multiple reaction monitoring mode (MRM) in negative ion mode. Each sample was injected in triplicate. Results: The assay was shown to be accurate and precise with %CV and % accuracy within ±15% of nominal across the full linear range (0.1 to 100 ng/mL). Conclusion: A fast, robust, and reliable method for the detection of barbiturates was developed. A simple dilute and shoot procedure was used for sample preparation. Limit of Quantitation (LOQ) for barbiturates were found to be around 0.1 ng/mL. doi:10.1016/j.clinbiochem.2011.06.043
P534 Root cause analysis of delays to discharge for patients held for serial cardiac troponin levels J.J. Owen, A. Worster, B.M. Waines, J. Ward, P. Kavsak, S. Hill Hamilton Health Sciences and McMaster University, Hamilton, ON, Canada Objective: Emergency department (ED) patients with suspected cardiac ischemia often remain in monitor beds for repeat cardiac troponin (cTn) levels to rule out non-ST-elevation myocardial infarction. We sought to identify root causes of delays to ED discharge. Methods: Two blinded data extractors reviewed the process event times of a random sample of ED patients discharged following a second cTn measurement during a one-year period. Process event times included time of ordering of second cTn, time of blood collection, time blood received in lab, time cTn results available, and time of ED discharge. Results: The analyses included 227 randomly selected cases from a total 9656 eligible patients. Mean time from ordering to time of ED discharge was 104.7 min (95% CI 95.3 to 114.0 min). Mean time for blood collection was 4.6 min (95% CI 8.9 to 0.4 min), mean transport time to lab was 15.0 min (95% CI 12.5 to 17.5 min), mean laboratory time was 49.1 min (95% CI 46.8 to 51.5 min), and mean time from results available to patient discharge was 45.2 min (95% CI 36.6 to 53.7). Conclusions: For ED patients held for second cTn levels, blood collection, transport, and laboratory processing times did not appear to be significant causes of delay. From time result available to time of ED discharge represents the largest modifiable time period on which to focus to minimize time patients remain in ED. doi:10.1016/j.clinbiochem.2011.06.045