Biweekly XELOX (capecitabine and oxaliplatin) as first-line treatment in elderly patients with metastatic colorectal cancer.

OBJECTIVE: The combination of oxaliplatin and oral capecitabine (XELOX) has shown to be an active regimen in metastatic colorectal cancer (MCRC). However, the experience with XELOX in elderly patients is limited. This study aimed to evaluate the efficacy and safety of XELOX as first-line treatment in elderly patients with MCRC. PATIENTS AND METHODS: Patients aged ≥70years with previously untreated MCRC received oxaliplatin 85mg/m(2) on day 1, every 2weeks plus capecitabine 1000mg/m(2) (or capecitabine 750mg/m(2) if creatinine clearance was 30-50mL/min) twice daily on days 1-7, every 2weeks. Treatment was continued until progression, intolerable toxicity, or for a maximum of 12cycles. RESULTS: Thirty-five patients were enrolled. Median age was 78years (range, 70-83). Patients received a median of 11cycles of treatment. The objective response rate (ORR) was 49% and the tumor control rate was 86%. Median time to progression and overall survival were 8.6 (95% CI: 5.5-11.7) and 15.5 (95% CI: 9.6-21.3) months, respectively. Toxicities were generally mild to moderate. Major grade 1-2 toxicities were asthenia (40%), nausea (43%), and diarrhea (40%). No grade 4 toxicity was detected and grade 3 toxicities were reported in 17% of patients. There was no treatment-related death. CONCLUSION: Our findings show that the biweekly XELOX regimen represents an effective and tolerable first-line treatment option for elderly patients with MCRC.

Determination of blood everolimus concentrations in kidney and liver transplant recipients using the sirolimus antibody conjugated magnetic immunoassay (ACMIA).

BACKGROUND: The aim of our study was to evaluate the possible determination of everolimus concentrations using the newly-introduced sirolimus antibody conjugated magnetic immunoassay (ACMIA). METHODS: Everolimus concentrations were determined in 100 blood samples from kidney (n = 47) and liver (n = 53) transplant recipients using the IMx sirolimus microparticle enzyme immunoassay (MEIA) from Abbott as previously described (Clin Biochem 2007;40:132-36) and sirolimus ACMIA from Siemens Healthcare Diagnostics Ltd. RESULTS: The ACMIA everolimus values were significantly higher than those of MEIA (p < 0.001). Analogous slope and intercept values were obtained in the linear regression between the ACMIA and MEIA results when compared to the Seradyn Certican everolimus controls or the blood samples from transplant recipients. Correction of the ACMIA values using the regression equation obtained for the control material (ACMIAcorrected = 0.55 ACMIA + 1.14) led to a satisfactory relationship with the results provided by the MEIA for the patients' samples (MEIA = 1.00 ACMIAcorrected + 0.30, r = 0.905, p < 0.001). CONCLUSIONS: The sirolimus ACMIA on the Dimension platform, which does not require manual pre-treatment of the blood samples, may be an acceptable option for therapeutic everolimus monitoring, significantly reducing technician time in comparison to other widely-used immunoassays.

Macromolecular complexes of cystatin C with circulating liver plasma membrane fragments and determination of serum cystatin C using the particle enhanced nephelometric immunoassay (PENIA) in kidney and liver transplantation and biliary obstruction.

BACKGROUND: In a patient with biliary obstruction, a macromolecular complex of cystatin C with liver plasma membrane fragments, which also contain several membrane-bound enzymes, which may be removed by butanol extraction, has recently been characterised. This could lead to an underestimation of the glomerular filtration rate (GFR) from serum cystatin C concentration. METHODS: Using the particle enhanced nephelometric immunoassay (PENIA), serum cystatin C concentration was determined in 50 healthy controls, 43 patients with renal insufficiency, 68 kidney and 88 liver transplant recipients, and 60 patients with biliary obstruction. Residual cystatin C concentrations and gamma-glutamyltransferase (GGT) activities after butanol extraction were also determined. RESULTS: In the controls and patients with renal insufficiency the residual concentrations of cystatin C after butanol extraction were always > or = 80%. However, in 2 renal and 7 liver transplant recipients and in 11 patients with biliary obstruction this biochemical variable was < 80%. A significant correlation between the residual cystatin C concentrations and residual GGT activities was obtained (r = 0.386, p < 0.001). In the relationship between estimated GFR from serum cystatin C and creatinine concentrations in the liver transplant recipients and patients with biliary obstruction, the 18 cases with residual cystatin C concentrations < 80% were included in the distribution of the total population data with no particular tendency. CONCLUSIONS: These results suggest that in the cases with residual cystatin C concentrations < 80% after butanol extraction, presumably due to the presence of circulating macromolecular cystatin C, the serum levels of cystatin C obtained using the PENIA assay do not lead to a systematic GFR underestimation.

A limited sampling strategy for estimation of the area under the curve (0 to 8 hours) of mycophenolic acid administered three times daily to liver transplant recipients.

OBJECTIVES: Gastrointestinal side-effects caused by mycophenolic acid (MPA) are frequent in liver transplant recipients, and in these cases a switch from two to three daily doses is usually recommended. However, a limited sampling strategy for the estimation of MPA area under the curve from 0 to 8 hours (AUC(0-8h)) has not been made. DESIGN AND METHODS: In 22 liver transplant patients who were administered MPA three times daily, the trapezoidal extrapolated MPA AUC(0-8h) values using a sampling time from 0 to 2 hours were calculated. RESULTS: A tentative therapeutic range for MPA AUC(0-8h) of about 20-40 µg.h/mL is proposed, and in the 13 patients with supratherapeutic values the total leukocyte blood count was significantly lower than in the 9 patients with AUC(0-8h) ≤ 40 µg.h/mL (P < 0.001). Significant negative correlations were found between the total leukocyte blood count and the MPA trough levels (r = -0.458; P < 0.05), AUC(0-8h) (r = -0.479; P < 0.05), and AUC(0-2h) (r = -0.437; P < 0.05). A significant correlation was found between the trapezoidal extrapolated AUC(0-8h) and trapezoidal AUC(0-2h) results (r = 0.850; P < 0.001). CONCLUSIONS: The trapezoidal extrapolated AUC(0-8h), and possibly trapezoidal AUC(0-2h), may be useful for routine therapeutic MPA monitoring in liver transplant recipients in which the dosing frequency is increased from twice to three times a day.

Sirolimus and everolimus clearance in maintenance kidney and liver transplant recipients: diagnostic efficiency of the concentration/dose ratio for the prediction of trough steady-state concentrations.

OBJECTIVES: Therapeutic monitoring of sirolimus and everolimus is necessary in order to minimize adverse side-effects and to ensure effective immunosuppression. A sirolimus-dosing model using the concentration/dose ratio has been previously proposed for kidney transplant patients, and the aim of our study was the evaluation of this single model for the prediction of trough sirolimus and everolimus concentrations. METHODS: Trough steady-state sirolimus concentrations were determined in several blood samples from each of 7 kidney and 9 liver maintenance transplant recipients, and everolimus concentrations from 20 kidney, 17 liver, and 3 kidney/liver maintenance transplant recipients. Predicted sirolimus and everolimus concentrations (Css), corresponding to the doses (D), were calculated using the measured concentrations (Css(0)) and corresponding doses (D(0)) on starting the study: Css = (Css(0))(D)/D(0). RESULTS: The diagnostic efficiency of the predicting model for the correct classification as subtherapeutic, therapeutic, and supratherapeutic values with respect to the experimentally obtained concentrations was 91.3% for sirolimus and 81.4% for everolimus in the kidney transplant patients. In the liver transplant patients the efficiency was 69.2% for sirolimus and 72.6% for everolimus, and in the kidney/liver transplant recipients the efficiency for everolimus was 67.9%. CONCLUSIONS: The model has an acceptable diagnostic efficiency (>80%) for the prediction of sirolimus and everolimus concentrations in kidney transplant recipients, but not in liver transplant recipients. However, considering the wide ranges found for the prediction error of sirolimus and everolimus concentrations, the clinical relevance of this dosing model is weak.

Glomerular filtration rate estimation using the Cockcroft-Gault and modification of diet in renal disease formulas for digoxin dose adjustment in patients with heart failure.

OBJECTIVE: The aim of this study was to compare the estimated glomerular filtration rate (GFR) using the Cockcroft-Gault and the 4-, 5-, and 6-variable Modification of Diet in Renal Disease (MDRD) formulas for digoxin dose adjustment. METHODS: Steady-state serum digoxin concentrations were determined in 100 patients with heart failure and normal to severely impaired renal function. Total clearance (CL) and predicted average concentrations of digoxin were calculated using general pharmacokinetic principles. RESULTS: The mean+/-SEM (median) estimated GFR values were 48.9+/-2.8 (46.5) mL/min/1.73 m(2) using the Cockcroft-Gault formula, 61.4+/-3.6 (56.4) mL/min/1.73 m(2) using the MDRD4 formula, 56.8+/-3.3 (52.1) mL/min/1.73 m(2) using the MDRD5 formula, and 53.3+/-3.0 (48.7) mL/min/1.73 m(2) using the MDRD6 formula, with high correlation coefficients between the estimates (r > or = 0.928, P < 0.001). Significant correlations were found between the digoxin total CL and estimated GFR by the Cockcroft-Gault (r = 0.649, P < 0.001), MDRD4 (r = 0.634, P <0.001), MDRD5 (r = 0.635, P < 0.001), and MDRD6 (r = 0.652, P < 0.001) formulas. A significant negative correlation of the digoxin total CL/GFR ratio with estimated GFR was obtained (r = -0.356, P < 0.001), with a high variability for this ratio for GFR lower than 60 mL/min. Analogous correlation coefficients were found between the obtained and predicted digoxin concentrations calculated using the estimated GFR by the Cockcroft-Gault (r = 0.628, P < 0.001), MDRD4 (r = 0.642, P < 0.001), MDRD5 (r = 0.650, P < 0.001), and MDRD6 (r = 0.665, P < 0.001) formulas, with a wide dispersion between the values in all cases. CONCLUSION: For GFR lower than 60 mL/min, the high interindividual variation of the digoxin total CL found among patients with similar renal function is an important limiting factor in the prediction of digoxin dosage regimens.

Determination of blood sirolimus concentrations in liver and kidney transplant recipients using the Innofluor fluorescence polarization immunoassay: comparison with the microparticle enzyme immunoassay and high-performance liquid chromatography-ultraviolet method.

BACKGROUND: Although high-performance liquid chromatography (HPLC) is the method of choice for blood sirolimus determination, the microparticle enzyme immunoassay (MEIA) run on the IMx analyser is widely used in therapeutic monitoring of this immunosuppressant agent. The aim of our study was to evaluate the possible determination of sirolimus using the fluorescence polarization immunoassay (FPIA) commercialized for everolimus quantification. METHODS: Sirolimus concentrations were determined in whole-blood samples from liver and kidney transplant recipients using the Innofluor Certican FPIA (Seradyn Inc.) run on a TDx analyser (Abbott Laboratories), Sirolimus MEIA run on an IMx analyser (Abbott Laboratories), and HPLC (UV detection) methods. RESULTS: The Innofluor FPIA has a similar cross-reactivity with everolimus and sirolimus, and the within- and between-run coefficients of variation obtained for sirolimus determination were 2.7%-13.3%. In analysing different blood samples from liver and kidney transplant patients the linear regressions obtained were: FPIA = 1.12 HPLC + 0.43 (n=104, r=0.874), MEIA = 1.14 HPLC (n=146, r=0.892), and FPIA = 1.00 MEIA + 0.29 (n=106, r=0.941). Better correlation coefficients were obtained between the methods in the liver transplant samples (r>or=0.900) than in the kidney transplant samples (r>or=0.849). No significant effect was found for sirolimus clearance or the blood hematocrit on the relationship between the results produced by both immunoassays and HPLC. CONCLUSION: The Innofluor FPIA is a valid alternative with an analogous performance to the MEIA for the therapeutic monitoring of sirolimus.

LDL cholesterol estimation using the Anandaraja's and Friedewald's formulas in schizophrenic patients treated with antipsychotic drugs.

OBJECTIVES: The use of new antipsychotic drugs is associated with an increased risk of diabetes and metabolic syndrome, and the routine monitoring of blood lipids during treatment has been recommended. Recently, a new formula for the estimation of low-density lipoprotein (LDL) cholesterol from total cholesterol and triglycerides has been proposed by Anandaraja et al. (Int J Cardiol 2005; 102: 117), and the aim of our study was its evaluation in schizophrenic patients treated with antipsychotic drugs. MATERIALS AND METHODS: In 487 serum samples from schizophrenic patients treated with clozapine in polytherapy, the concentrations of LDL cholesterol were determined by agar gel electrophoresis and the formula of Friedewald et al. (Clin Chem 1972; 18: 499), and compared with the results of the Anandaraja's formula. RESULTS: A higher correlation and lower error of the estimate of the electrophoresis results was found with those of Friedewald (r=0.940, ma68=0.17 mmol/L) than those of Anandaraja (r=0.811, ma68=0.31 mmol/L). Similar results were obtained on making a dichotomy of the patients with and without metabolic syndrome lipid profile. A highly significant correlation was found between the high-density lipoprotein (HDL) cholesterol levels and the Anandaraja/Electrophoresis (r=0.817, p<0.001) and Anandaraja/Friedewald (r=0.977, p<0.001) ratios. CONCLUSIONS: According to our data, Anandaraja's formula tends towards an overestimation or underestimation of LDL cholesterol levels, depending on whether the HDL cholesterol levels are high or low, which may be clinically significant. These results do not support the proposed better accuracy of the Anandaraja's than the Friedewald's formula.

Evaluation of three dosing models for the prediction of steady-state trough clozapine concentrations.

OBJECTIVE: Therapeutic drug monitoring of clozapine may be useful for the clinical management of schizophrenic patients treated with this atypical antipsychotic drug. The aim of our study was the evaluation of three models for the prediction of steady-state trough clozapine concentration. PATIENTS AND METHODS: The trough serum concentrations of clozapine and norclozapine were determined by high-performance liquid chromatography in 296 samples from a group of 21 schizophrenic patients selected for their good therapeutic compliance. Also, the predicted clozapine concentrations were estimated by applying the models of Oyewumi et al. (Ther Drug Monit 1995; 17: 137), Perry et al. (Biol Psychiatry 1998; 44: 733) and Rostami-Hodjegan et al. (J Clin Psychopharmacol 2004; 24: 70). RESULTS: The efficiency for the accurate estimation of clozapine concentrations as subtherapeutic (<240 ng/mL), therapeutic (240-750 ng/mL) or supratherapeutic (>750 ng/mL), using the models of Oyewumi et al., Perry et al., and Rostami-Hodjegan et al., was 82%, 71% and 77% respectively. CONCLUSIONS: The predictive model of Oyewumi et al., which shows an easy calculation way and the greater diagnostic efficiency, may be of clinical value for the prediction of clozapine concentration or the dose required to achieve a specified concentration.

Chitotriosidase activity in pleural effusions.

Chitotriosidase (ChT) is mainly secreted by monocyte-derived macrophages, and is considered a useful marker of macrophage activation. Macrophages represent the first line of defence against Mycobacterium tuberculosis, and consequently the study of ChT activity in pleural effusions (PE) would be of clinical value in the laboratory characterization of tuberculous pleurisy. ChT and adenosine deaminase (ADA) activities were determined in 12 tuberculous PE, 26 non-tuberculous lymphocytic PE and 25 neutrophilic PE. The enzyme heterogeneity study for ChT was made by thermal inactivation at 60 degrees C according to Wajner et al. (Clin Biochem 2004;37:893). ChT activity was significantly higher in the group of tuberculous PE than in the non-tuberculous lymphocytic PE group (p < 0.01), although no significant difference was found with respect to neutrophilic PE. The correlation between ChT and ADA was statistically significant, although in the partial correlation keeping the protein concentration constant, statistical significance was only achieved in tuberculous and non-tuberculous lymphocytic PE (r = 0.358, p < 0.05). In lymphocytic PE, a ChT activity greater than 40 mmol/h/mL has a sensitivity of 92%, specificity of 72%, and efficiency of 78% for the biochemical characterization of tuberculous pleurisy. Residual activities obtained for ChT by heat inactivation did not make it possible to differentiate the enzyme isoforms in PE presumably secreted by macrophages and polymorphonuclear leukocytes.

Determination of everolimus in whole blood using the Abbott IMx sirolimus microparticle enzyme immunoassay.

OBJECTIVES: Everolimus (Certican) is a new immunosuppressant derived from sirolimus (Rapamune) with a 2-hydroxyethyl chain at position 40 of the macrolide ring. The aim of our study was to evaluate the possible determination of everolimus in whole blood using a commercialized microparticle enzyme immunoassay for sirolimus determination. DESIGN AND METHODS: Everolimus concentrations were determined in blood samples from 11 kidney transplant patients (n=51) and different control materials (n=35) using the Seradyn Innofluor Certican fluorescence polarization immunoassay (FPIA) and the Abbott IMx sirolimus microparticle enzyme immunoassay (MEIA). RESULTS: The MEIA gave a concentration-dependent cross-reactivity with the everolimus, with a linear regression between the assigned values (y) for the Innofluor Certican calibrators and those obtained (x) using this immunoassay: y=0.96x+0.67 (ma68=0.21 microg/L, r=0.974, p<0.001). The within- and between-run coefficients of variation using the MEIA were

Effect of the hematocrit and its correction on the relationship between blood tacrolimus concentrations obtained using the microparticle enzyme immunoassay (MEIA) and enzyme multiplied immunoassay technique (EMIT).

The Abbott microparticle enzyme immunoassay (MEIA) and the Dade Behring enzyme multiplied immunoassay technique (EMIT) are the most frequently used methods in the therapeutic drug monitoring of tacrolimus; however, a hematocrit-dependent interference for the MEIA has been described. In 244 whole blood samples from patients with liver (n=152) and kidney (n=92) transplants, the MEIA/EMIT ratio presented a highly significant negative correlation with the hematocrit (r = -0.482, p < 0.001). On distributing the samples into three groups with a hematocrit of less than 30%, 30-40%, and higher than 40%, different regression equations were found between the results of MEIA and EMIT and demonstrate the different effect of the hematocrit on both immunoassays. Correcting the MEIA results by calculation for a hematocrit of less than 30% and higher than 40% (Hermida et al. Clin Lab 2005; 51: 43-45) led to a regression with EMIT that was similar to that found between MEIA and EMIT for the group of samples with a hematocrit of 30-40%. Furthermore, the corrected MEIA/EMIT ratio had a poor correlation with the hematocrit (r = 0.149, p < 0.05). In 95 samples with a hematocrit of less than 25% (n=73) and higher than 40% (n=22) we also determined the tacrolimus levels using the modified MEIA method to correct hematocrit interference, as proposed by Tomita et al. (Ther Drug Monit 2005; 27: 94-97). In the samples with a hematocrit of less than 25%, correcting the MEIA results by calculation produced results that were similar and had a high correlation coefficient (r = 0.954, p < 0.001) to those of the modified MEIA method, whose application as a routine practice is more expensive and laborious. Calculation of the corrected MEIA values in anemic patients may be useful for the therapeutic monitoring of tacrolimus.

Effect of analytical inaccuracy on dose adjustment for gentamicin using the Abbottbase Pharmacokinetic Systems.

We studied the effect of analytical inaccuracy on the determination of gentamicin for estimation of the recommended dose regime (RDR) using the Abbottbase Pharmacokinetic System programme (PKS). The study was carried out in a group of 26 adult patients, determining their serum levels of gentamicin (Cmin and one hour after completing infusion, C1h) and these concentrations were processed using the PKS in order to establish the RDR (dose, posologic interval and infusion time) for each patient. Various simulations were made for each patient, adding and subtracting the clinically acceptable error (CAE) once, twice and three times to the experimentally determined Cmin and the estimated Cmax. The simulated dose regime (SDR) was calculated for each patient. The number of cases in which the SDR differed from the RDR were determined, and also the percentage of variation of the SDR with respect to the RDR. A highly significant correlation was found between C1h and the estimated Cmax (r = 0.941, p < 0.001). A statistically significant difference (p < 0.05) and a clinically significant difference were found between both populations of concentrations, and so the simulations were carried out using the estimated Cmax. A frequency of change of 29.87% was recorded in the RDR, and inaccuracies of +/- CAE in the Cmin and Cmax led to changes of the RDR in 21.2% of the cases studied. A higher frequency of change in the RDR was observed in additive-type simulations for Cmax, with this change mainly affecting the dose, and in subtractive-type simulations for Cmin, with this change affecting both the dose and the posologic interval. An inaccuracy of the order of +/- CAE in the serum concentrations of gentamicin (both for Cmin and Cmax) frequently led to changes in the RDR, thus requiring precise and accurate concentration results, particularly in the case of Cmin. For this reason, we would suggest the convenience of using a previous moment in the time concentration level in the monitoring of gentamicin instead of Cmin, which would be determined with greater imprecision and inaccuracy.

Chitotriosidase activity in plasma and mononuclear and polymorphonuclear leukocyte populations.

In the general population, about 5% of individuals are homozygotic and 35% are heterozygotic carriers for chitotriosidase (ChT) deficiency. Activated macrophages are considered to be the main source of plasma ChT activity, which permits the biochemical characterization of homozygote deficients. However, in the case of detecting heterozygotic carriers, the results are often inconclusive. The activities of ChT in plasma and mononuclear (MN) and polymorphonuclear (PMN) leukocytes were determined in 169 control subjects (72 males and 97 females) with a mean age (+/- SD) of 47.5+/-9.7 years (range 18-96 years). The specific enzyme activity was in PMN leukocytes >MN leukocytes >plasma, with a highly significant partial correlation being found between the activities of ChT in plasma and PMN leukocytes (r=0.578, P<0.001). A significant correlation was found between the age of the patients studied and plasma ChT activity (r=0.568, P<0.001). No significant correlation was found for enzyme activities in MN (r=0.105) or in PMN leukocytes (r=0.043). The results obtained suggest that, in normal physiological conditions, PMN leukocytes may secrete ChT to the plasma. Although the activities of ChT in MN and PMN leukocytes are not affected by demographic factors, it is not possible to use them for the biochemical detection of ChT-deficient heterozygotic carriers.