Suitability of Becton Dickinson Vacutainer rapid serum tube for collecting and storing blood samples for antibiotic and anticonvulsant drug monitoring.

AIMS: To investigate the suitability of newly developed Becton Dickinson Vacutainer rapid serum tube (RST) for therapeutic drug monitoring of antibiotics and anticonvulsants. METHODS: Two pools of citrated whole blood were created by spiking high and low concentrations of gentamicin, vancomycin, phenytoin, lamotrigine and carbamazepine. After recalcification with 15 mmol/L calcium chloride, spiked whole blood was added into four different Becton Dickinson blood collection tubes: RST, serum separator tube, red top tube and polyethylene plain tube. Serum aliquots were collected at baseline (0 h), 2 h, 24 h, day 3 and day 7. Drug concentrations were measured in batch by HPLC and the Architect c8000. RESULTS: Gentamicin and vancomycin concentrations were stable up to 7 days in all 4 blood collection tubes. Anticonvulsants results for the RST were stable and did not deviate substantially from those of the red top and plain tubes, and demonstrated better performance than the serum separator tubes that showed significant (≥10% bias, p<0.05) decrease in phenytoin and carbamazepine levels after 3 days of storage. CONCLUSIONS: The RST provides acceptable drug stability over the course of 7 days for gentamicin, vancomycin, phenytoin and lamotrigine and over 3 days for carbamazepine.

Free testosterone: clinical utility and important analytical aspects of measurement.

Testosterone, the most abundant androgen in men, is a steroid hormone that is synthesized predominantly by the testes. In women, minor amounts are synthesized in the ovaries. Androgen precursors are also produced and secreted from the adrenal glands in both sexes, where they undergo peripheral conversion to testosterone. Circulating concentrations are approximately 15-25 times higher in adult men compared to women. Maintenance of these levels is necessary for development and maintenance of secondary sexual characteristics, libido, growth, prevention of osteoporosis, and most importantly in men, spermatogenesis. Most testosterone circulates tightly bound to sex hormone-binding globulin (SHBG) or weakly bound to albumin. A minor amount circulates as free testosterone, and it is believed that this is the metabolically active fraction. Measurement of free testosterone is important in the diagnosis of many diseases, most importantly disorders of androgen deficiency in men (i.e., hypogonadism) and androgen excess in women (i.e., polycystic ovary syndrome and hirsutism). Many methodologies are available for free testosterone measurement including the reference methods (equilibrium dialysis and ultrafiltration), analog immunoassay, and calculated free testosterone based on measurement of total testosterone, SHBG, and albumin. Moreover, measurement of bioavailable testosterone, a combination of albumin-bound and free testosterone, also has clinical utility and can be measured by selective protein precipitation or calculation. In this review, the advantages and limitations of each of these methods will be discussed in the context of clinical utility and implementation into a routine hospital laboratory. Furthermore, up and coming methodologies for free testosterone measurement, including liquid chromatography-tandem mass spectrometry, will also be discussed.

Advance targeted transfusion in anemic cardiac surgical patients for kidney protection: an unblinded randomized pilot clinical trial.

INTRODUCTION: : Acute kidney injury (AKI) is a serious complication of cardiac surgery, and preoperative anemia and perioperative erythrocyte transfusion are important risk factors. Prophylactic erythrocyte transfusion in anemic patients may, therefore, protect against AKI. METHODS: : In this unblinded, parallel-group, randomized pilot trial, 60 anemic patients (hemoglobin 10-12 g/dL) undergoing cardiac surgery with cardiopulmonary bypass were randomized (1:1) to prophylactic transfusion (2 units of erythrocytes transfused 1 to 2 days before surgery (n = 29) or standard of care (transfusions as indicated; n = 31). Between-group differences in severity of perioperative anemia, transfusion, and AKI (more than 25% drop in estimated glomerular filtration rate) were measured. The relationships between transfusion, iron levels, and AKI were also measured. RESULTS: : Perioperative anemia and erythrocyte transfusions were lower in the prophylactic transfusion group--median (25th, 75th percentiles) for nadir hemoglobin was 8.3 (7.9, 9.1) versus 7.6 (6.9, 8.2) g/dL (P = 0.0008) and for transfusion was 0 (0, 2) versus 2 (1, 4) units (P = 0.0002)--but between-group AKI rates were comparable (11 patients per group). In 35 patients with iron studies, perioperative transfusions were directly related to postoperative transferrin saturation (correlation coefficient 0.6; P = 0.0002), and high (more than 80%) transferrin saturation was associated with AKI (5/5 vs. 8/30; P = 0.005), implicating transfusion-related iron overload as a cause of AKI. CONCLUSIONS: : In anemic patients, prophylactic erythrocyte transfusion reduces perioperative anemia and erythrocyte transfusions, and may reduce plasma iron levels. Adequately powered studies assessing the effect of this intervention on AKI are warranted.

Influence of erythrocyte transfusion on the risk of acute kidney injury after cardiac surgery differs in anemic and nonanemic patients.

BACKGROUND: Acute kidney injury (AKI) after cardiac surgery is a major health issue. Two important risk factors for AKI are preoperative anemia and perioperative erythrocyte transfusion, and elucidating their relationship may help in devising preventive strategies. METHODS: In this cohort study of 12,388 adults who underwent cardiac surgery with cardiopulmonary bypass and received three units or less of erythrocytes on the day of surgery, the authors used propensity score methods and conditional logistic regression to explore the relationship between preoperative anemia (hemoglobin less than 12.5 g/dL), erythrocyte transfusion on the day of surgery, and AKI (more than 50% decrease in estimated glomerular filtration rate from preoperative to postoperative day 3-4). RESULTS: AKI occurred in 4.1% of anemic patients (n = 94/2,287) and 1.6% of nonanemic patients (n = 162 of 10,101) (P < 0.0001). In the 2,113 propensity-score matched pairs, anemic patients had higher AKI rates than nonanemic patients (3.8% vs. 2.0%; P = 0.0007). AKI rates increased in direct proportion to the amount of erythrocytes transfused, and this increase was more pronounced in anemic patients: in anemic patients, the rate increased from 1.8% among those not transfused to 6.6% among those transfused three units (chi-square test for trend P < 0.0001), whereas in nonanemic patients, it increased from 1.7% among those not transfused to 3.2% among those transfused three units (chi-square test for trend P = 0.1). CONCLUSIONS: Anemic patients presenting for cardiac surgery are more susceptible to transfusion-related AKI than nonanemic patients. Interventions that reduce perioperative transfusions may protect anemic patients against AKI.

The novel immunoregulatory molecule FGL2: a potential biomarker for severity of chronic hepatitis C virus infection.

BACKGROUND & AIMS: This report describes the use of a novel sensitive and specific ELISA for the measurement of human fibrinogen-like protein 2 (FGL2/fibroleukin), a novel effector of natural regulatory T (Treg) cells, to predict the course of chronic hepatitis C viral infection (HCV). METHODS: Plasma levels of FGL2 were measured in HCV patients and compared to healthy controls and to patients with alcoholic liver disease. RESULTS: FGL2 levels were significantly higher in HCV patients (84.3+/-89.1 ng/ml, n=80) compared to healthy controls (36.4+/-21.9 ng/ml, n=30, p<0.001), to a subset of patients who cleared HCV following anti-viral treatment (16.6+/-19.7 ng/ml, n=32, p<0.001), and to patients with inactive alcoholic liver disease (18.8+/-17.4 ng/ml, n=24, p<0.001). Among HCV patients, plasma levels of FGL2 correlated significantly with the stage of fibrosis (p=0.001) and were significantly higher in patients with cirrhosis (164.1+121.8 ng/ml, n=60) compared to non-cirrhotics (57.7+/-52.8 ng/ml, n=20, p=0.001). Genotype 1 patients had significantly higher levels of FGL2 (98.1+/-100.3 ng/ml, n=60) compared to patients with genotype 2/3 (41.5+/-38.6 ng/ml, n=20, p=0.0008). Patients with genotype 2/3 had FGL2 levels similar to healthy controls (41.5+/-38.6 vs. 36.41+/-21.9 ng/ml, p=ns). Infiltrating lymphocytes in liver biopsies of HCV patients were positive for either FGL2 or FoxP3 (a marker of Treg cells) or expressed both markers. CONCLUSIONS: This report documents the development of a sensitive ELISA for measurement of plasma levels of FGL2 an effector Treg cells, which correlates with the severity of HCV infection.

Evaluation of the ARCHITECT urine NGAL assay: assay performance, specimen handling requirements and biological variability.

OBJECTIVES: NGAL (Neutrophil Gelatinase-Associated Lipocalin) has emerged as a new biomarker for the identification of acute kidney injury. Reliable clinical evaluations require a simple, robust test method for NGAL, and knowledge of specimen handling and specimen stability characteristics. We evaluated the performance of a new urine NGAL assay on the ARCHITECT analyzer. METHODS: Assay performance characteristics were evaluated using standard protocols. Urine specimen storage requirements were determined and biological variability was assessed in a self-declared apparently healthy population. RESULTS: Assay performance data showed good precision, sensitivity and lot-to-lot reproducibility. There was good short term 2-8 degrees C sample stability, however, long term storage samples must be kept at -70 degrees C or colder. The largest variance component in a biological variance study was within-day. CONCLUSIONS: The ARCHITECT NGAL assay proved to be a precise and reproducible assay for the determination of urine NGAL.

Direct measurement of serum free testosterone by ultrafiltration followed by liquid chromatography tandem mass spectrometry.

BACKGROUND: Currently there is no reliable method suitable for routine measurement of serum free testosterone (FT). AIM: To develop such a method involving liquid chromatography tandem mass spectrometry (LC-IDMS/MS) that directly detects and quantifies the FT present in serum. METHODS: Ultrafiltrate testosterone obtained from 0.5 mL of serum was partially purified by liquid/liquid extraction and quantified using an Agilent 1200 Series HPLC system coupled to an API 5000 mass spectrometer equipped with an atmospheric pressure chemical ionization ion source. Using split samples serum free testosterone was compared between direct ultrafiltration (UF) coupled LC-MS/MS, analogue FT immunoassay, free testosterone calculated from mass action equations (cFT) and with equilibrium dialysis (ED) coupled LC-MS/MS. RESULTS: Total imprecision determined over twenty runs was <6% at 67 pmol/L and 158 pmol/L FT. The dynamic response was linear up to at least 2500 pmol/L while physical LLOQ (18 % CV) equaled 16 pmol/L. The UF method agreed poorly with analogue immunoassay (correlation coefficient 0.667; bias -81%), somewhat better against cFT when total testosterone was determined by immunoassay (correlation coefficient 0.816, bias 21% ) and still better yet against cFT when total testosterone was determined by LC-MS/MS (correlation coefficient 0.8996, bias 10%). Agreement was closest with ED method (correlation coefficient 0.9779, bias 2.4%). CONCLUSION: We present a relatively simple UF coupled LC-MS/MS definitive method that measures serum free testosterone. The method is relatively fast, reliable and is suitable for the routine clinical laboratory practice.

Rapid determination of serum testosterone by liquid chromatography-isotope dilution tandem mass spectrometry and a split sample comparison with three automated immunoassays.

OBJECTIVES: To develop a rapid convenient-to-implement high performance liquid chromatography-isotope dilution tandem mass spectrometry (LC-IDMS/MS) method for determination of serum testosterone concentration in routine clinical laboratories. METHODS: Following extraction by organic solvents, an Agilent 1200 Series HPLC system coupled to an API 5000 mass spectrometer equipped with an atmospheric pressure chemical ionization ion source was used to separate, detect and quantify serum testosterone. Ion-transitions of m/z 289.2-->109.1 and 294.2-->113.2 were used to monitor testosterone and testosterone-2,2,4,6,6-d(5), respectively. RESULTS: Functional sensitivity was 0.056 nmol/L (CV 20%). Within-run and total imprecision were 4.6% and 5.2% at 1.3 nmol/L, 2.4% and 4.3% at 11.0 nmol/L, and 1.9% and 1.9% at 23.4 nmol/L respectively. The LC-MS/MS method agreed closely with three automated immunoassays when the concentration of testosterone exceeded 3 nmol/L. However, the immunoassays showed a positive bias at concentrations below 3 nmol/L. CONCLUSION: This method provides a rapid, simple, highly selective and sensitive procedure that can be easily used for determination of serum testosterone in routine clinical laboratories. It measures serum testosterone precisely and accurately at concentrations found in children and adults of both genders.

Metabolic syndrome features and risk of neural tube defects.

BACKGROUND: Maternal obesity and pre-pregnancy diabetes mellitus, features of the metabolic syndrome (MetSyn), are individual risk factors for neural tube defects (NTD). Whether they, in combination with additional features of MetSyn, alter this risk is not known. We evaluated the risk of NTD in association with maternal features of the MetSyn. METHODS: We used a population-based case-control study design in the province of Ontario, Canada. Cases and controls were derived from women who underwent antenatal maternal screening (MSS) at 15 to 20 weeks' gestation. There were 89 maternal cases with, and 434 controls without, an NTD-affected singleton pregnancy. Maternal features of MetSyn were defined by the presence of pre-pregnancy diabetes mellitus, body weight > or = 90th centile among controls, non-white ethnicity and/or serum highly sensitive C-reactive protein (hsCRP) > or = 75th centile of controls. Since hsCRP naturally increases in pregnancy, analyses were performed with, and without, the inclusion of hsCRP in the model. RESULTS: Mean hsCRP concentrations were exceptionally high among study cases and controls (6.1 and 6.4 mg/L, respectively). When hsCRP was excluded from the model, the adjusted odds ratios for NTD were 1.9 (95% confidence interval 1.1-3.4) in the presence 1 feature of MetSyn, and 6.1 (1.1-32.9) in the presence of 2 or more features. When hsCRP was included, the respective risk estimates were attenuated to 1.6 (0.88-2.8) and 3.1 (1.2-8.3). CONCLUSION: We found about 2-fold and 6-fold higher risk for NTD in the presence 1, and 2 or more features, of the metabolic syndrome, respectively. It is not clear whether this risk is altered by the presence of a high serum hsCRP concentration.

Vitamin B12 and the risk of neural tube defects in a folic-acid-fortified population.

BACKGROUND: Low maternal vitamin B(12) status may be a risk factor for neural tube defects (NTDs). Prior studies used relatively insensitive measures of B(12), did not adjust for folate levels, and were conducted in countries without folic acid food fortification. In Canada, flour has been fortified with folic acid since mid-1997. METHODS: We completed a population-based case-control study in Ontario. We measured serum holotranscobalamin (holoTC), a sensitive indicator of B(12) status, at 15 to 20 weeks' gestation. There were 89 women with an NTD and 422 unaffected pregnant controls. A low serum holoTC was defined as less than 55.3 pmol/L, the bottom quartile value in the controls. RESULTS: The geometric mean serum holoTC levels were 67.8 pmol/L in cases and 81.2 pmol/L in controls. There was a trend of increasing risk with lower levels of holoTC, reaching an adjusted odds ratio of 2.9 (95% confidence interval = 1.2-6.9) when comparing the lowest versus highest quartile. CONCLUSIONS: There was almost a tripling in the risk for NTD in the presence of low maternal B(12) status, measured by holoTC. The benefits of adding synthetic B(12) to current recommendations for periconceptional folic acid tablet supplements or folic-acid-fortified foods need to be considered. It remains to be determined what fraction of NTD cases in a universally folate-fortified environment might be prevented by higher periconceptional intake of B(12).