Pui-Yuen Wong

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.

Detection of Prostate Cancer Relapse With Prostate Specific Antigen Monitoring at Levels of 0.001 to 0.1 micro g./l

PURPOSE The development of prostate specific antigen (PSA) assays with detection limits of approximately 0.001 microgram./l. is technically feasible. We examined if serum PSA changes of 0.001 to 0.1 microgram./l. for up to 3 years after radical prostatectomy have any clinical value. MATERIALS AND METHODS We studied 148 patients with a postoperative PSA of less than 0.1 microgram./l. by a conventional PSA assay. At least 3 serial serum samples were collected per patient along with detailed clinicopathological features. Serial serum samples were analyzed for PSA with the ultrasensitive method. Associations between increase in serum PSA and clinicopathological features were analyzed with the unconditional logistic regression model. RESULTS After establishing a set of interpretative criteria, we divided the patients into 51 with biochemical relapse, 93 who were free of relapse and 4 with equivocal status. Between the groups with and without relapse there was no difference in year of surgery, age at operation or length of followup. Compared to patients without relapse, those with biochemical relapse were likely to have positive surgical margins (p < 0.01), larger tumor volumes (p < 0.01), greater preoperative PSA (p = 0.03) and disease extending outside the prostate (p = 0.02). The relative risks for biochemical relapse estimated by a univariate logistic regression model were 3.1 (95% confidence interval 1.39 to 6.82, p < 0.01) for positive surgical margin, 3.4 (95% confidence interval 1.46 to 8.13, p < 0.01) for tumor volume, 2.3 (95% confidence interval 1.08 to 5.02, p = 0.03) for high preoperative PSA and 2.7 (95% confidence interval 1.12 to 6.26, p = 0.03) for extraprostatic tumor extension. At multivariate analysis with the same model the associations between positive surgical margins and biochemical relapse (relative risk 2.95, p = 0.04) and tumor volume (relative risk 3.36, p = 0.03) remained significant. These associations were still observed when we analyzed a subset of patients classified as having biochemical relapse based on PSA changes of 0.001 to 0.08 microgram./l. CONCLUSIONS Increases in postoperative serum PSA at levels of 0.001 to 0.1 microgram./l. after radical prostatectomy are associated with clinicopathological features of poor prognosis. Monitoring postoperative cases with a highly sensitive PSA assay (detection limit 0.001 microgram./l.) could offer a simple and effective means of detecting clinically important biochemical relapse early after radical prostatectomy. These patients may be suitable for early intervention when effective treatments for relapse become available.

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.

Pharmacokinetics of a new oral formulation of cyclosporine in liver transplant recipients.

Trough concentrations of cyclosporine can be highly variable because of its poor bioavailability in current oral formulations, Sandimmune (SIM). Neoral (N-SIM) a new microemulsion of cyclosporine is more readily absorbed than SIM in healthy controls. The present study compared the pharmacokinetic profiles of SIM and N-SIM following orthotopic liver transplantation. In 16 patients with partial biliary diversion, 1 week after transplantation, the bioavailability and peak concentration of a single 300 mg dose of N-SIM were greater than SIM by 724% (p = 0.0019) and 800% (p = 0.0001), respectively. In 39 patients who were on stable doses of cyclosporine 1 month after transplantation, the bioavailability of N-SIM was higher than that of SIM under both fasting ( + 64%, p = 0.001) and fed ( + 37%, p = 0.004) conditions. Trough concentrations were similar for the two formulations. However, peak concentrations were higher for N-SIM in both fasting ( + 119%, p = 0.003) and fed ( + 53%, p = 0.003) patients. Also, time to peak was shorter for N-SIM in both fasting (-21%, p = 0.027) and fed (-59%, p = 0.0001) patients. The correlation between trough concentrations and bioavailability was greater for N-SIM than for SIM in fasted (r = 0.80, p = 0.0001 versus r = 0.75, p = 0.0001) and fed patients (r = 0.65; p = 0.002 versus r = 0.55; p = 0.012). We conclude that the rate of absorption and the bioavailability of N-SIM is significantly and consistently better than SIM and-may, therefore, improve the therapeutic index of cyclosporine after liver transplantation.

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.

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.

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.

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.

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.