Transaction Management in Database Management System
Gardner, lynn (atlanta_3)[1][1]
1. Accuracy of Oral Fluid Lead Testing Lynn Gardner, MD, Emory University Atlanta Georgia; Robert Geller, MD, Emory University Atlanta Georgia; Robyn Hannigan, Ph.D. University of Massachusetts; Yu Sun, MD, MPH Ga. Department of Community Health; Anil Mangla, M.S.,Ph.D., MPH. FRIPH, Ga. Department of Community Health
2. Disclaimer Drs. Gardner, Geller, and Mangla are independent evaluators of this lab method and have no conflicts of interest with this lab methodology or with any vendor of testing services.
9. Limitations The prevalence of lead poisoning in the study cohort was less than the national average of 1.5% Due to the small number of elevated blood lead levels, the performance characteristics of this test at higher blood lead levels was not established.
10. This study compares oral fluid lead levels and blood lead levels in a clinical setting.
12. Methods Oral fluid samples collected on 500 children aged 6 months old to 5 years old Children having venous blood lead levels drawn for routine screening purposes were eligible.
13. Methods The blood lead levels were measured using standard methodology at a CLIA certified laboratory. The oral fluid lead levels were measured using an ICP-MS (DRC II, PerkinElmer Sciex). Oral fluid samples from 50 children were gathered twice to provide internal controls, but were only counted once.
14. Methods The mean absolute difference between the sample groups was determined to test the hypothesis that group means are equal.
15. Results Five hundred patients agreed to enroll. No eligible patient declined to participate. 474 patients had both blood and oral fluid samples available for analysis. 26 did not have blood available.
22. Data Results 9/474 patients were identified as false positives (1.9%) 0/474 patients were missed as false negatives (0%)
23. Determining Cut-Off values A sensitive test is positive when a disease is present A specific test is usually negative when a patient is disease free Higher sensitivity of a test is associated with fewer false negatives To establish a cut-off value, determine the test characteristics to assess highest sensitivity with highest specificity
25. Conclusions Oral fluid may be a reliable medium to use when screening children for lead exposure for levels < 4mcg/dL. Oral fluid lead levels ≥ 4mcg/dL should be confirmed by a venous blood sample. The sample size in the ≥ 4mcg/dL group (n=19) was inadequate to draw conclusions on accuracy at higher lead levels. Further studies are being conducted.
49. Oral Fluid Lead Proficiency Correlation 27 pairs of samples were analyzed by an ICP-MS for saliva and blood lead for each individual patient.
50. Method Detection Limit Performed at the start ofeach daily analytical run 7 individual standards comprised of a “spiked” swabcontaining 0.30 ug/dL Pb Standard Deviation of 7measurements * Student-t for n=6 at 99% confidence 15 MDL determinationsMDL = 0.006 +/- 0.002 ug/dL Pb(0.06 ng Pb per mL fluid) Calibration data using external calibration standards (n=6) and blank, Internal standard (20 ppb In), instrument configuration (EPA 6020, DRC II ICP-MS, no cell gas).
51. METHODS Standard Operating Procedure – EPA 6020 for ICP-MS with the following modifications Indium as single internal standard, 6 calibration standards (0.1 to 10 ug/dL Pb), 2 QA/QC standards (0.2, 7.0 ug/dL), run allowed to proceed if R2 > 0.999, QA/QC stds within 95% of known. Concentration of standards (2% ultrapure HNO3) entered in software as ug/dL to allow for direct reporting of results in appropriate units, blank subtracted prior to quantification, all Pb counts per second normalized to In counts per second prior to quantification by the software. Matrix suppression study revealed logarithmic response of detector to higher matrix concentrations, correction factor applied for dilutions during sample preparation and matrix effect (total dissolved solids) = 1.639log(counts per second Pb/In) Digestion blanks also analyzed every 10 samples (see outline of methods) = below method detection limit All data processing, calibrations, and QA/QC handled by PerkinElmer software (EPA 6020 methods adapted for use in this project)
Editor's Notes
Linear Range tested 1.0 to 50 mcg/dLPrecision at 10mcg/dL = 100% and at 50mcg/dL = 98%Correlation R2 = 0.999
7 Samples were tested each day for 3 days to calculate reproducibility
Post trial initial oral fluid and blood lead correlations show means are statistically similar p< 0.05
Calibration curve for standards. NOTE – we did not use matrix matched standards. We did try this approach by spiking swabs with known amounts of Pb and In diluted in 1% diastase but the issues of matrix suppression (as discussed on last slide) made this approach untenable given the analytical time constraints in the lab. Most assuredly this needs to be assessed in terms of whether this increases accuracy. Above is a calibration curve averaging 59 independent calibrations from our analytical runs. Symbols (circles) do have x and y errors on them barely extending past the symbol size. The 95% confidence interval shows the reproducibility of our analytical calibrations. We propogated error in sample measurements with these propogated errors reported to Anil as std deviations (in fact they are propagated standard errors).
Should be self explanatory I hope. Additional comments on next slide.
Notes – we did NOT have the luxury of a full scale analytical study to adequately assess matrix suppression issues at lower concentrations. Though the blank swab Pb concentrations are below our method detection limit we report what we call “oral fluid” Pb concentrations but do not know the actual volume of oral fluid in the sample and so in reality are reporting the concentration of the sample swab tip mass and NOT the actual volumetrically defined oral fluid concentration. The analytical details of the ICP-MS analysis, for the ICP-MS users who may be there are as follows: Reaction Gas – none, RF voltage 1400, Pulse Detector voltage 900, Analog Detector Voltage -1850, nebulizer gas flow 0.97 mL/min, plasma gas (Argon) gas flow 15 L/min. Instrument operation parameters for tuning: background at 220 amu and 8.5 amu < 3 counts per second (cps), tuning solution 1 ppb Mg, Co, In, Ba, Ce, Pb. Mg cps > 6000, In cps > 100,000, Pb cps > 100,000. Dual detector calibration, autolens calibration performed each analytical day. Mass calibration performed as part of monthly instrument maintenance. Autosampler – Cetac ASX520. All samples prepared under laminar flow in a class 100 clean room. All acids were ultrapure, all reagent water 18.3 MegOhm. All digestion vessels acid washed teflon, all pipette tips acid washed upon receipt and disposed of (not re-used).
