Adherence to Azathioprine/6-Mercaptopurine in Children and Adolescents with Inflammatory Bowel Diseases: A Multimethod Study.

Background: Measurement of the degree of adherence is a key element for the evaluation of treatment efficacy and safety; thus, adherence plays an important role in clinical research and practice. The aim of this study was to investigate medication adherence in children with inflammatory bowel disease (IBD) utilizing a multimethod assessment approach. A further aim was to examine factors that can influence adherence within this population. Methods: Medication adherence in 47 children (age range 3 to 17 years) with IBD in three centers in Northern Ireland and Jordan was assessed via subjective (parent and child versions of the Medication Adherence Report Scale (MARS) specific questionnaire) and objective methods, that is, high-performance liquid chromatography (HPLC) determination of the 6-mercaptopurine (6-MP) and azathioprine (AZA) metabolites in packed red blood cell samples taken during a clinic visit. Beliefs about prescribed medicines were also assessed in parents/guardians using the Beliefs about Medicines Questionnaire (BMQ). Results: An overall nonadherence to AZA/6-MP therapy in children with IBD was found to be 36.17% (17 out of 47 patients were classified as nonadherent using at least one of the assessment methods). A total of 41 patients (91.1%) were classified as adherent to AZA or 6-MP using the blood sampling, while adherence rates using the MARS questionnaire completed by children and parents/guardians were 60.6% and 72.7%, respectively. The latter provides a more longitudinal measure of adherence. Child self-reported nonadherence rates were significantly higher than parent/guardian reported rates (p=0.013). Binary logistic regression analysis identified age to be independently predictive of adherence, with adolescents (children aged ≥ 13 years old) more likely to be classified as nonadherent. Regarding the BMQ, when parental/guardian necessity beliefs outweighed concerns, that is, higher scores in the necessity-concern differential (NCD), adolescents were more likely to be classified as adherent. Conclusion: Results provide evidence for ongoing adherence challenges in the paediatric population with IBD. It is recommended that parents/guardians (particularly of older children) and older children themselves, should receive enhanced counselling and education about their prescribed medicines.

Determination of azathioprine/6-mercaptopurine metabolites in dried blood spots: Correlation with RBC concentrations.

The analysis of 6-thioguanine (6-TG) and 6-methylmercaptopurine (6-mMP) in biological samples is not straight forward and requires pre-treatment of samples. There are no validated published methods for the analysis of azathioprine/6-mercaptopurine (AZA/6-MP) metabolites in dried blood spot (DBS) samples that study the correlation with red blood cells (RBC) concentrations. DBS was prepared by applying fifteen microliters of blood [spiked with analytes or samples obtained from patients] to a Guthrie card which was then dried at room temperature overnight. The sample treatment procedure used protein precipitation followed by a hydrolysis step in which, 6-mMP was converted into 4-amino-5-(methylthio)carbonyl imidazole (AMTCI) then analytes were transferred to a solid phase extraction cartridge. The extracted sample was chromatographed using a reversed phase system (C18) column preceded by a guard column of matching chemistry. The method gave a linear calibration over the range 0.5-15 µmol/L and 3.75-175 µmol/L for 6-TG and 6-mMP, respectively. The method has been applied successfully to the determination of 6-TG and 6-mMP concentrations in DBS finger-prick samples from 27 paediatric patients with IBD who were receiving (AZA/6-MP). Patient 6-TG and 6-mMP RBC concentrations, calculated from whole blood finger prick DBS samples and those measured in RBCs derived from matched venous samples (analyzed using conventional HPLC-UV technique) showed good agreement using the Bland-Altman test. This is the first published method for determining 6-TG and 6-mMP in DBS that studies their correlation with RBCs concentrations. It is applicable to a range of clinical studies such as adherence and pharmacokinetic studies involving AZA/6-MP.

Highly sensitive and rapid determination of azathioprine metabolites in whole blood lysate by liquid chromatography-tandem mass spectrometry.

Individualized therapy involves genetic test of drug metabolism, which provides information about the initial dose and therapeutic drug monitoring for adjusting the subsequent dose. Consequently, toxic side effects are expected to be minimized and therapeutic effects to be maximized. In this study, an ultra-performance liquid chromatography tandem mass spectrometry method that was specific, accurate and sensitive was developed to simultaneously determine azathioprine two metabolites, 6-thioguanine nucleotides (6-TGN) and 6-methyl-mercaptopurine riboside (6-MMPr) in the whole blood lysate. We precipitated the sample by trifluoroacetic acid under the protection of dithiothreitol, with 6-MMPr and 6-TGN being hydrolyzed to produce 6-methymercaptopurine and 6-thioguanine. In the chromatographic separation, Waters ACQUITY BEH C18 (2.1 × 100 mm, 1.7 µm) chromatographic column was applied and gradient elution was conducted with 0.02 mol/L ammonium acetate buffer (which contains 0.3% formic acid) and acetonitrile at a flow rate of 0.4 ml/min. Tandem mass spectrometry in multiple reaction monitoring mode was applied for detection via electrospray ionization source in positive ionization mode. The analyzing process lasted for no more than 2 min. The calibration curve for each metabolite fitted a least squares model (weighed 1/X) from 1.25 to 5000 ng/ml (r2 > 0.99). The ion pairs were detected as 6-MMP m/z 167.07 â†’ 152.15, 6-TG m/z 168.06 â†’ 134.13, and internal standard m/z 171.07 â†’ 137.14. Under the guidance of FDA guidelines for bioanalytical method validation, we carried out validation and obtained satisfactory results. The method was successfully utilized for monitoring the concentrations of each metabolite from 65 affected patients who had received azathioprine maintenance therapy and achieved optimal results.

Do clinical and laboratory parameters predict thiopurine metabolism and clinical outcome in patients with inflammatory bowel diseases?

PURPOSE: The thiopurines azathioprine and 6-mercaptopurine are frequently used for remission maintenance in patients with inflammatory bowel diseases. However, there are therapy failures, and it is unclear whether clinical and laboratory parameters can be used to predict thiopurine metabolite concentrations (as a surrogate for adequate remission maintenance therapy) and clinical outcome in these patients. METHODS: In this retrospective analysis of clinical routine patient data, multivariate statistical models based on Linear Mixed Models regression and Generalized Estimating Equations logistic regression were developed. The adequacy of the models was assessed using Pearson's correlation and a receiver operating characteristic curve. RESULTS: This study included 273 patients and 1158 thiopurine metabolite measurements as well as routine laboratory and clinical data. In the statistical models, thiopurine metabolite concentrations and the odds of non-remission based on different clinical and laboratory parameters were computed. Correlation (r2) between predicted and measured thiopurine metabolites were 0.40 (p < 0.001) for 6-thioguanine nucleotides and 0.53 (p < 0.001) for 6-methyl-mercaptopurine nucleotides, respectively. The model for remission classified data sets in remission and non-remission with a sensitivity of 63% and a specificity of 73%. The area under the receiver operating characteristic curve of the model was 0.72. CONCLUSIONS: Although the models are not yet accurate enough to be used in clinical routine, model-based prediction of thiopurine metabolite concentrations and of outcome is feasible. Until more accurate models are developed and validated, traditional therapeutic drug monitoring of thiopurine metabolites in patients with inflammatory bowel diseases under thiopurine therapy stays the best tool to individualize therapy.

Sperm DNA Integrity is Unaffected by Thiopurine Treatment in Men With Inflammatory Bowel Disease.

BACKGROUND AND AIMS: Sperm DNA integrity, concentration, and motility are suspected to be altered by thiopurines (azathioprine [AZA] and 6-mercaptopurine [6-MP]). We investigated the impact of thiopurines on semen quality in men with inflammatory bowel disease [IBD], by a comprehensive panel of semen analyses. METHODS: Semen from 40 men with IBD, in remission on AZA/6-MP therapy, was prospectively collected and compared with samples from 40 healthy volunteers. Paired samples [off and on AZA/6-MP] were obtained from a subset of IBD patients, and blood and semen were collected to determine 6-MP transmission to the ejaculate. Sperm DNA fragmentation was evaluated via sperm chromatin structure assay [SCSA] and Comet analysis. Conventional World Health Organization [WHO] parameters, i.e. semen volume and sperm concentration, motility, and morphology, were assessed. Additionally, we measured thioguanine nucleotide [TGN] incorporation in sperm cell DNA. RESULTS: Sperm DNA fragmentation levels did not differ between men with IBD on AZA/6-MP and healthy volunteers when evaluated by SCSA [p = 0.23] and Comet analysis [p = 0.72]. IBD patients on AZA/6-MP had significantly lower total and progressive sperm motility than healthy volunteers [48.5% versus 64.5%, p = 0.0003; 27.4% versus 43.3%, p = 0.0004; respectively], with no differences in concentration, volume, or morphology. The same trend was observed in the 10 paired samples. TGN incorporation was not detectable in sperm DNA, but 6-MP was detected in seminal plasma and correlated to blood levels [rs = 0.79, p = 0.02]. CONCLUSIONS: Thiopurines do not increase sperm DNA fragmentation but may impair sperm motility in this IBD cohort. Our findings support existing epidemiological data that thiopurine therapy is safe during preconception and should not be abandoned.

Fecal calprotectin is significantly linked to azathioprine metabolite concentrations in Crohn's disease.

BACKGROUND: The value of therapeutic drug monitoring during azathioprine (AZA) therapy with respect to clinical outcomes has been convincingly demonstrated in recent meta-analyses. However, the association between AZA metabolites and the mucosal state in inflammatory bowel disease is largely unclear. AIMS: We investigated the association between AZA's active metabolite 6-thioguanine nucleotides (6-TGN) and fecal calprotectin (FC) as a well-validated surrogate marker of mucosal inflammation in patients with Crohn's disease (CD) on AZA monotherapy. PATIENTS AND METHODS: Of 443 6-TGN measurements, 140 values from 88 patients with CD on AZA monotherapy visiting the inflammatory bowel disease outpatient clinic between 2009 and 2016 were retrospectively analyzed. In a subcohort with serial 6-TGN measurements, longitudinal FC measurements in patients with versus without intervention (dose increase, allopurinol, and education) were assessed. RESULTS: In patients with 6-TGN concentrations within a predefined range (250-450 pmol/8×10 red blood cells), FC was significantly lower (median: 119.5 vs. 327.2 mg/kg, P=0.003), and hemoglobin as well as serum protein concentrations were significantly higher than in patients with 6-TGN outside of this range. C-reactive protein and transferrin saturation were not different. In the longitudinal cohort, 6-TGN increased in the intervention group, but only a minority reached the defined range; no significant change in FC was observed. CONCLUSION: This study is the first to show that in patients with CD receiving AZA monotherapy, 6-TGN concentrations within a defined range (250-450 pmol/8×10 red blood cells) are associated with significantly lower FC. A treat-to-target concept directed by 6-TGN to reach mucosal healing may thus be a promising approach (DRKS00013246).

Therapeutic Drug Monitoring in Pediatric Inflammatory Bowel Disease.

PURPOSE OF REVIEW: Therapeutic drug monitoring (TDM) has emerged as a useful tool to optimize the use of drug therapies in adults with inflammatory bowel disease (IBD), including both Crohn's disease (CD) and ulcerative colitis (UC), especially during the use of biological therapies, for which the pharmacokinetics and pharmacodynamics are highly variable among patients. Fewer data exist in children. This review examines the current literature on TDM in pediatric IBD. RECENT FINDINGS: Drug clearance is affected by a number of patient and disease factors. For thiopurines, adjusting dosing by monitoring 6-thioguanine (6TGN) and 6-methylmercaptopurine ((6MMP) levels is demonstrated to maximize response and minimize toxicity, while monitoring metabolite levels when treating with anti-tumor necrosis factor (anti-TNF) remain controversial. While in adults the use of TDM in the setting of loss of response to anti-TNF therapy is established, in children, only a small number of studies exist, but these too have encouraging results. There are however, conflicting data regarding the optimal timing of TDM, comparing "reactive" monitoring and "proactive" monitoring. No such data exist in pediatrics. TDM is cost-effective, and dose reduction may represent a safety benefit. There are limited adult data for use of TDM for the newer biologics, vedolizumab and ustekinumab, but early results suggest similarly promising utility. The use of TDM in pediatric IBD is increasing in clinical practice, with similar efficacy to adults demonstrated in children with loss of response to anti-TNF therapy. More prospective studies are needed in children to examine proactive monitoring and utility of TDM with newer biologics.

Therapeutic Drug Monitoring in Pediatric IBD: Current Application and Future Perspectives.

BACKGROUND: as the paradigm for IBD management is evolving from symptom control to the more ambitious goal of complete deep remission, the concept of personalized medicine, as a mean to deliver individualized treatment with the best effectiveness and safety profile, is becoming paramount. Therapeutic drug monitoring (TDM) is an essential part of personalized medicine and its role in the management of IBD patients is rapidly expanding. OBJECTIVE: to review the current knowledge that poses the rationale for the use of TDM, and the present and future role of TDM-based approaches in the management of pediatric IBD. METHOD: literature review. RESULTS: the concept of TDM has been introduced in the field of IBD along with thiopurines, over a decade ago, and evolved around anti-TNF therapies. TDM-based strategies proved to be costeffective in the management of patients with loss of response to biologics and, more recently, proactive TDM to optimize drug exposure has been shown to reduce treatment failure and drug adverse events. The role of TDM with new biologics and the usefulness of software-systems support tools to guide drug dosing are now under investigation. CONCLUSION: Therapeutic drug monitoring has the potential to maximize the cost-benefit profile of therapies and is becoming an essential part of IBD management.

Analytical Pitfalls of Therapeutic Drug Monitoring of Thiopurines in Patients With Inflammatory Bowel Disease.

The use of thiopurines in the treatment of inflammatory bowel disease (IBD) can be optimized by the application of therapeutic drug monitoring. In this procedure, 6-thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine (6-MMP) metabolites are monitored and related to therapeutic response and adverse events, respectively. Therapeutic drug monitoring of thiopurines, however, is hampered by several analytical limitations resulting in an impaired translation of metabolite levels to clinical outcome in IBD. Thiopurine metabolism is cell specific and requires nucleated cells and particular enzymes for 6-TGN formation. In the current therapeutic drug monitoring, metabolite levels are assessed in erythrocytes, whereas leukocytes are considered the main target cells of these drugs. Furthermore, currently used methods do not distinguish between active nucleotides and their unwanted residual products. Last, there is a lack of a standardized laboratorial procedure for metabolite assessment regarding the substantial instability of erythrocyte 6-TGN. To improve thiopurine therapy in patients with IBD, it is necessary to understand these limitations and recognize the general misconceptions in this procedure.

American Gastroenterological Association Institute Technical Review on the Role of Therapeutic Drug Monitoring in the Management of Inflammatory Bowel Diseases.

Therapeutic drug monitoring (TDM), which involves measurement of drug or active metabolite levels and anti-drug antibodies, is a promising strategy that can be used to optimize inflammatory bowel disease therapeutics. It is based on the premise that there is a relationship between drug exposure and outcomes, and that considerable inter-individual variability exists in how patients metabolize the drug (pharmacokinetics) and the magnitude and duration of response to therapy (pharmacodynamics). Therefore, the American Gastroenterological Association has prioritized clinical guidelines on the role of TDM in the management of inflammatory bowel disease. To inform these clinical guidelines, this technical review was developed in accordance with the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) framework for interventional and prognostic studies, and focused on the application of TDM for biologic therapy, specifically anti-tumor necrosis factor-α agents, and for thiopurines. Focused questions address the benefits and risks of a strategy of reactive TDM (in patients with active inflammatory bowel disease) to guide treatment changes compared with empiric treatment changes, and the benefits and risks of a strategy of routine proactive TDM (during routine clinical care in patients with quiescent disease) compared with no routine TDM. Additionally, the review addresses the benefits and risks of routine measurement of thiopurine methyltransferase enzyme activity or genotype before starting thiopurine therapy compared with empiric weight-based dosing and explores the performance of different trough drug concentrations for anti-tumor necrosis factor agents and thiopurines to inform clinical decision making when applying TDM in a reactive setting. Due to a paucity of data, this review does not address the role of TDM for more recently approved biologic agents, such as vedolizumab or ustekinumab.

Thiopurine metabolites variations during co-treatment with aminosalicylates for inflammatory bowel disease: effect of N-acetyl transferase polymorphisms.

AIM: To evaluate variation of the concentration of thiopurine metabolites after 5-aminosalicylate (5-ASA) interruption and the role of genetic polymorphisms of N-acetyl transferase (NAT) 1 and 2. METHODS: Concentrations of thioguanine nucleotides (TGN) and methymercaptopurine nucleotides (MMPN), metabolites of thiopurines, were measured by high performance liquid chromatography in 12 young patients (3 females and 9 males, median age 16 years) with inflammatory bowel disease (6 Crohn's disease and 6 ulcerative colitis) treated with thiopurines (7 mercaptopurine and 5 azathioprine) and 5-ASA. Blood samples were collected one month before and one month after the interruption of 5-ASA. DNA was extracted and genotyping of NAT1, NAT2, inosine triphosphate pyrophosphatase (ITPA) and thiopurine methyl transferase (TPMT) genes was performed using PCR assays. RESULTS: Median TGN concentration before 5-ASA interruption was 270 pmol/8 x 10(8) erythrocytes (range: 145-750); after the interruption of the aminosalicylate, a 35% reduction in TGN mean concentrations (absolute mean reduction 109 pmol/8 × 10(8) erythrocytes) was observed (median 221 pmol/8 × 10(8) erythrocytes, range: 96-427, P value linear mixed effects model 0.0011). Demographic and clinical covariates were not related to thiopurine metabolites concentrations. All patients were wild-type for the most relevant ITPA and TPMT variants. For NAT1 genotyping, 7 subjects presented an allele combination corresponding to fast enzymatic activity and 5 to slow activity. NAT1 genotypes corresponding to fast enzymatic activity were associated with reduced TGN concentration (P value linear mixed effects model 0.033), putatively because of increased 5-ASA inactivation and consequent reduced inhibition of thiopurine metabolism. The effect of NAT1 status on TGN seems to be persistent even after one month since the interruption of the aminosalicylate. No effect of NAT1 genotypes was shown on MMPN concentrations. NAT2 genotyping revealed that 6 patients presented a genotype corresponding to fast enzymatic activity and 6 to slow activity; NAT2 genotypes were not related to thiopurine metabolites concentration in this study. CONCLUSION: NAT1 genotype affects TGN levels in patients treated with thiopurines and aminosalicylates and could therefore influence the toxicity and efficacy of these drugs; however the number of patients evaluated is limited and this has to be considered a pilot study.

Risk factors and incidence for lipid abnormalities in kidney transplant patients.

BACKGROUND: Lipid abnormalities (LA) are related to an increased risk for cardiovascular diseases in kidney transplantation patients. PATIENTS AND METHODS: Multivariable logistic regression models were used to estimate the risk of LA associated with potential risk factors, including immunosuppressant use, patient background characteristics, and laboratory data. RESULTS: In total, 386 patients who were undergoing kidney transplantation were included in the study. Statins were prescribed to 43% of patients. The LA composite outcome was defined as statin use and/or low density lipoprotein cholesterol level ≥120 mg/dL, and 229 patients (59.3%) developed LA as a result. LA was significantly related to everolimus, corticosteroid, age, and estimated glomerular filtration ratio in the multiple logistic regression analysis. The odds ratios were 2.264, 3.119, 1.186, and 0.870, respectively. Mycophenolate mofetil, mizoribine, azathioprine, cyclosporine (CYA), tacrolimus, proteinuria, body mass index, and male sex were not related to LA. DISCUSSION: CYA influenced lipid metabolism but was not related to LA in our study. The mean post transplantation period was 8.4 years, and the CYA dose decreased over time. The CYA blood concentration was 70.0 ng/mL, which is relatively low, but it decreased the susceptibility to LA. Serum lipid levels were well controlled by statins, and the estimated glomerular filtration rate was maintained stably. CONCLUSIONS: Everolimus and corticosteroid use, as well as a lower estimated glomerular filtration rate and higher age, were significant risk factors for LA. CYA is known for its adverse LA effects, but it was not a significant risk factor for LA in patients undergoing maintenance phase kidney transplantation.

Hematologic indices as surrogate markers for monitoring thiopurine therapy in IBD.

BACKGROUND: Clinical efficacy and risk of complications are associated with intracellular levels of thiopurine metabolites 6-thioguanine nucleotides (6-TGN) and 6-methylmercaptopurines (6-MMP) in patients with Crohn's disease. Therapeutic monitoring of thiopurine metabolites is not widely available. Surrogate markers such as hematologic indices (MCV, leukopenia) have been proposed. AIMS: To evaluate accuracy of hematologic indices for prediction of therapeutic levels of thiopurine metabolites. METHODS: A retrospective cross-sectional study. We included patients treated with thiopurines for IBD between February 2008 and November 2013. Hematologic indices were correlated with thiopurine metabolites and compared to pre-treatment levels. RESULTS: A total of 168 patients with 608 measurements were included. Macrocytosis was observed in 4.5 % of the patients. On multivariate analysis, macrocytosis was associated with 6-TGN levels >235 pmol/8 × 10(8) erythrocytes and 6-mmp levels >5,700 pmol/8 × 10(8) erythrocytes. Therapeutic 6-TGN levels were associated with MCV, ΔMCV, macrocytosis and lymphocyte count. Sensitivity and Spearman's r correlation for prediction of therapeutic metabolite levels were poor for all hematologic indices. CONCLUSION: Although macrocytosis and an elevated MCV are associated with therapeutic 6-TGN levels, the correlation is weak. None of the evaluated hematologic indices is a reliable surrogate marker for thiopurine metabolite levels.

Novel assay to improve therapeutic drug monitoring of thiopurines in inflammatory bowel disease.

BACKGROUND AND AIMS: The thiopurines are widely used in the treatment of inflammatory bowel disease, but are limited by poor dose-effect relationship. The objective was to assess the ability of a novel assay, determining the mono-, di-, and triphosphates, of thioguanine as well as methylthioinosine as individual metabolites in erythrocytes, to predict clinical outcome compared to a routine assay, determining metabolites as sums. METHODS: Samples from 79 patients with Crohn's disease or ulcerative colitis treated with azathioprine or mercaptopurine were analysed by both assays. Clinical status was determined by the Harvey-Bradshaw and Walmsley indices. The genotypes of thiopurine methyltransferase (TPMT) and inosine triphosphatase were determined. RESULTS: TPMT wild-type patients with thioguanine nucleotide (TGN) levels below the cut-off level were more likely to have active disease when TGN was measured by the novel assay (p=0.02), and when thioguanosine triphosphate (TGTP) was measured separately (p=0.01). When TGN was measured by the routine assay the correlation was not evident (p=0.12). Neither TGN levels nor TGTP correlated to disease activity in TPMT deficient patients. Patients with methyl thioinosine nucleotide (meTIN) levels above 1500 pmol/8×10^8 RBCs were more likely to have active disease (p=0.07). We observed good correlations between the mono-, di-, and triphosphates and their respective sums (R(2)>0.88). CONCLUSIONS: The novel TGN assay was better in predicting clinical outcome compared to the routine assay, while determination of TGTP had no clinical advantage and TGTP ratio was not correlated to disease activity.

Routine use of thiopurines in maintaining remission in pediatric Crohn's disease.

AIM: To evaluate the effectiveness of thiopurines in maintaining steroid-free remission in routine clinical practice. METHODS: The multi-center Pediatric Inflammatory Bowel Disease Network (PIBDNet) cohort study prospectively collected data on thiopurine naïve patients initiating mercaptopurine (6MP) or azathioprine. Patients with a diagnosis of Crohn's disease (CD) were included in our study upon entering remission as determined by physician global assessment (PGA) within 365 d of initiation of thiopurines. The primary outcome of the study was maintenance of steroid-free remission (SFR) at each follow up visit. Patients were considered treatment failures if there had been a change in PGA from remission to mild, moderate or severe disease; disease relapse between visits; need for rescue therapy (biologic therapy, methotrexate, steroids); thiopurine discontinuation, hospitalization or surgical intervention. A secondary outcome defined treatment failure as a change from remission to moderate or severe (not mild) in addition to the previously defined criteria. RESULTS: Sixty-five of 182 patients in the PIBDNet registry met criteria for inclusion in this study. Forty-five of 65 (69%) of included patients achieved remission within 180 d of thiopurine initiation. For the primary outcome, 47% and 23% of patients remained in SFR at 6 and 12 mo. The mean thiopurine dose at initiation for the 65 included patients was 0.89 ± 0.31 mg/kg per day. Metabolite levels were obtained in 48% (31/65) of the included patients with a mean 6TG level of 258 pmole/8 × 10(8) RBC ± 147. For the secondary outcome, 65% and 42% of patients remained in SFR at 6 and 12 mo. CONCLUSION: Thiopurines were less effective in maintaining remission for pediatric CD in this "real world" cohort than has been previously described. Variation in thiopurine dosing and metabolite measurement was found among practitioners.

Seroconversion of 2009 pandemic influenza A (H1N1) vaccination in kidney transplant patients and the influence of different risk factors.

BACKGROUND: Influenza may present a high morbidity and mortality in solid organ transplanted patients (SOTP). Annual influenza virus vaccine is recommended for SOTP. However, low levels of seroconversion in SOTP have been reported. The aim of this study was to evaluate the immunogenicity of 2009 pandemic influenza A (H1N1) - A(H1N1)pdm09--vaccine in kidney transplant patients and to analyze which features might affect seroconversion. METHODS: This study was conducted from March to August 2010 at the Renal Transplantation Unit of University of São Paulo, Brazil. A total of 85 renal transplant patients attending the outpatient unit received one 15-µg intramuscular dose of A(H1N1) pdm09 influenza vaccine (reassortant vaccine virus A/California/7/2009 [NYMC X-179A]). Blood samples were collected immediately before and 21 days after the vaccine was given. Antibody response was measured by the standard hemagglutination-inhibition (HI) assay. The primary immunogenicity endpoint for this study was seroconversion in previously seronegative patients (HI titers <1:40), and the secondary endpoint was the identification of features that could affect seroconversion in this population. RESULTS: Five (5.9%) patients presented HI titers prevaccination ≥ 1:40 and were excluded from further analysis. Seroconversion in previously negative patients occurred in 27 (34%) of 80 patients. Prevaccination HI titers geometrical mean was 5.8 and postvaccination 19.6 (ratio 3.4). Significant seroconversion rate factors were female gender, non-Caucasian ethnicity, and post-transplant time before vaccination. No impact was seen on seroconversion for age, donor type, tacrolimus and cyclosporine blood levels, renal function, or blood lymphocyte counts. Mycophenolate (MPA) showed a lower rate of seroconversion when compared with azathioprine. Tacrolimus and cyclosporine had similar seroconversion rates. Sirolimus use was associated with the highest rate of seroconversion, although these patient numbers were low. Immunosuppresssion containing MPA was considerably less effective in seroconversion than drug combinations with no MPA. Patients receiving sirolimus had more chance of seroconversion. HI titers geometric means pre/post vaccine were as follows: MPA (n = 56): 5.8/12.8; tacrolimus (n = 50): 5.9/16.2; cyclosporine (n = 18): 5.4/24.2; azathioprine (n = 19): 6.2/51.6; and sirolimus (n = 6): 8/80. By univariate analysis, being female and non-White were variables associated with 3.3 times more chance of seroconversion than being male and White. In the multivariate analysis, the variables remaining in the model showed similar hazard ratios. CONCLUSIONS: In this study, the monovalent A(H1N1)pdm09 influenza vaccine demonstrated low rates of seroconversion, particularly in patients on MPA, but with potentially higher response rates in patients on sirolimus.

Monitoring of thiopurine metabolites - a high-performance liquid chromatography method for clinical use.

A high-performance liquid chromatography method capable of measuring thiopurine mono-, di-, and triphosphates separately in red blood cells (RBCs) was developed. RBCs were isolated from whole blood using centrifugation. Proteins were precipitated using dichloromethane and methanol. The thioguanine nucleotides (TGNs) were derivatised using potassium permanganate before analysis. Analytes were separated by ion-pairing liquid chromatography using tetrabutylammonium ions and detected using UV absorption and fluorescence. The method was designed for use in clinical trials. Ten patient samples were analysed to demonstrate clinical application and to establish pilot ranges for all analytes. The method measured thioguanosine mono-(TGMP), di-(TGDP), and triphosphate (TGTP), as well as methylthioinosine mono- (meTIMP), di- (meTIDP) and triphosphate (meTITP) in RBCs collected from patients treated with thiopurine drugs (azathioprine, 6-mercaptopurine, and 6-thioguanine). LOQ was 0.3, 3, 2, 30, 30 and 40 pmol/8 × 108 RBC, for TGMP, TGDP, TGTP, meTIMP, meTIDP and meTITP, respectively. Between-day precision were below 14% for all analytes at all concentrations and samples were stable at 4 °C for 8 h after sampling.