Multi-laboratory validation of a Δ9-tetrahydrocannabinol LC-MS/MS test kit designed for quantifying THC and marijuana metabolites in blood.

Marijuana legalization has increased the demand for testing of Δ9-tetrahydrocannabinol (THC) and THC metabolites. The THC ToxBox® test kit (THC ToxBox®) is commercially available and supports high-throughput LC-MS/MS analytical methods designed to quantify low levels of THC and THC metabolites in blood. The purpose of this study is to determine if this new test kit meets the rigors of laboratory accreditation and produces equivalent results across six states- and locally-funded laboratories. Each laboratory followed internal method validation procedures established for their clinical (CLIA) or international (ISO17025) accreditation program. Test performance indicators included accuracy, precision, measurement of uncertainty, calibration models, reportable range, sensitivity, specificity, carryover, interference, ion suppression/enhancement and analyte stability. Analytes and interferents were resolved within the 6-min analytical runtime, and the 48-well plate pre-manufactured with calibrators, second source quality control material, and internal standards at precise concentrations allowed for simple and consistent sample preparation in less than one hour. Every laboratory successfully validated test kit procedures for forensic use. Differences in sensitivity were generally associated with the use of older equipment. Statistical analysis of results spanning reportable ranges show that laboratories with different instrument platforms produce equivalent results at levels sufficiently low enough to support per se limit testing of THC and THC metabolites (1-5 ng/mL). THC ToxBox® represents a viable option for state- and locally-funded laboratories charged with investigating impaired driving cases involving marijuana use.

Ferritin trends do not predict changes in total body iron in patients with transfusional iron overload.

Ferritin levels and trends are widely used to manage iron overload and assess the efficacy of prescribed iron chelation in patients with transfusional iron loading. A retrospective cohort study was conducted in 134 patients with transfusion-dependent anemia, over a period of up to 9 years. To determine whether the trends in ferritin adequately reflect the changes in total body iron, changes in ferritin between consecutive liver iron measurements by magnetic resonance imaging (MRI) were compared to changes in liver iron concentrations (LIC), a measure of total body iron. The time period between two consecutive LIC measurements was defined as a segment. Trends in ferritin were considered to predict the change in LIC within a segment if the change in one parameter was less than twofold that of the other, and was in the same direction. Using the exclusion criteria detailed in methods, the trends in ferritin were compared to changes in LIC in 358 segments. An agreement between ferritin trends and LIC changes was found in only 38% of the 358 segments examined. Furthermore, the change in ferritin was in opposite direction to that of LIC in 26% of the segments. Trends in ferritin were a worse predictor of changes in LIC in sickle cell disease than in thalassemia (P < 0.01). While ferritin is a convenient measure of iron status; ferritin trends were unable to predict changes in LIC in individual patients. Ferritin trends need to be interpreted with caution and confirmed by direct measurement of LIC.

Tissue iron evaluation in chronically transfused children shows significant levels of iron loading at a very young age.

Chronic blood transfusions start at a very young age in subjects with transfusion-dependent anemias, the majority of whom have hereditary anemias. To understand how rapidly iron overload develops, we retrospectively reviewed 308 MRIs for evaluation of liver, pancreatic, or cardiac iron in 125 subjects less than 10 years old. Median age at first MRI evaluation was 6.0 years. Median liver iron concentrations in patients less than 3.5 years old were 14 and 13 mg/g dry weight in thalassemia major (TM) and Diamond-Blackfan anemia (DBA) patients, respectively. At time of first MRI, pancreatic iron was markedly elevated (> 100 Hz) in DBA patients, and cardiac iron ( R2* >50 Hz) was present in 5/112 subjects (4.5%), including a 2.5 years old subject with DBA. Five of 14 patients (38%) with congenital dyserythropoietic anemia (CDA) developed excess cardiac iron before their 10th birthday. Thus, clinically significant hepatic and cardiac iron accumulation occurs at an early age in patients on chronic transfusions, particularly in those with ineffective or absent erythropoiesis, such as DBA, CDA, and TM, who are at higher risk for iron cardiomyopathy. Performing MRI for iron evaluation in the liver, heart, and pancreas as early as feasible, particularly in those conditions in which there is suppressed bone marrow activity is very important in the management of iron loaded children in order to prescribe appropriate chelation to prevent long-term sequelae. .

Longitudinal analysis of heart and liver iron in thalassemia major.

High hepatic iron concentration (HIC) is associated with cardiac iron overload. However, simultaneous measurements of heart and liver iron often demonstrate no significant linear association. We postulated that slower rates of cardiac iron accumulation and clearance could reconcile these differences. To test this hypothesis, we examined the longitudinal evolution of cardiac and liver iron in 38 thalassemia major patients, using previously validated magnetic resonance imaging (MRI) techniques. On cross-sectional evaluation, cardiac iron was uncorrelated with liver iron, similar to previous studies. However, relative changes in heart and liver iron were compared with one another using a metric representing the temporal delay between them. Cardiac iron significantly lagged liver iron changes in almost half of the patients, implying a functional but delayed association. The degree of time lag correlated with initial HIC (r = 0.47, P < .003) and initial cardiac R2* (r = 0.57, P < .001), but not with patient age. Thus, longitudinal analysis confirms a lag in the loading and unloading of cardiac iron with respect to liver iron, and partially explains the weak cross-sectional association between these parameters. These data reconcile several prior studies and provide both mechanical and clinical insight into cardiac iron accumulation.