[Development of hospital pharmacy practice using therapeutic drug monitoring]

Therapeutic drug monitoring (TDM) is a developing field in hospital pharmacy that contributes to good clinical response. Optimal concentrations of immunosuppressants, anti-epileptic drugs, and glycopeptide antibiotics are narrow, and these drugs are widely monitored by fluorescence polarization immunoassay (FPIA) in clinical settings. Recently, a chemiluminescence immunoassay (CLIA) has also become available. We compared these two assays in monitoring serum concentrations of cyclosporin A (CsA), carbamazepine (CBZ), phenobarbital, phenytoin, and valproic acid. FPIA estimates of CsA and CBZ concentrations were higher than CLIA estimates. We also evaluated the two methods' cross-reactions to metabolites. The FPIA, but not the CLIA, method was affected by metabolites. We conclude that CLIA has adequate precision and accuracy for use in routine therapeutic drug monitoring in clinical situations. We also report a case of meningitis caused by methicillin-resistant Staphylococcus epidermidis (MRSE) in a neonatal girl. The patient had intraventricular hemorrhage and was treated with ventricular drainage. Because MRSE was detected in her cerebrospinal fluid (CSF), vancomycin (VCM) was administered intravenously, but had no beneficial effect. Subsequent treatment with linezolid (LZD) successfully ameliorated her CSF cell count and protein levels. These results indicate that LZD may be a treatment option for neonates and infants for drain-associated meningitis caused by MRSE. In conclusion, TDM can determine drug concentration and indicate optimal pharmaceutical approach for treatment.

Multisite analytical evaluation of the Abbott ARCHITECT cyclosporine assay

The objective of this study was to evaluate the analytical performance of the Abbott ARCHITECT Cyclosporine (CsA) immunoassay in 7 clinical laboratories in comparison to liquid chromatography/tandem mass spectrometry (LC/MS/MS), Abbott TDx, Cobas Integra 800, and the Dade Dimension Xpand immunoassay. The ARCHITECT assay uses a whole blood specimen, a pretreatment step with organic reagents to precipitate proteins and extract the drug, followed by a 2-step automated immunoassay with magnetic microparticles coated with anti-CsA antibody and an acridinium-CsA tracer. Imprecision testing at the 7 evaluation sites gave a range of total % coefficient of variations of 7.5%-12.2% at 87.5 ng/mL, 6.6%-14.3% at 411 ng/mL, and 5.2%-10.7% at 916 ng/mL. The lower limit of quantification ranged from 12 to 20 ng/mL. Purified CsA metabolites AM1, AM1c, AM4N, AM9, and AM19 were tested in whole blood by the ARCHITECT assay and showed minimal cross-reactivity at all 7 sites. In particular, AM1 and AM9 cross-reactivity in the ARCHITECT assay, ranged from -2.5% to 0.2% and -0.8% to 2.2%, respectively, and was significantly lower than for the TDx assay, in which the values were 3.2% and 16.1%, respectively. Comparable testing of metabolites in the Dade Dimension Xpand assay at 2 evaluation sites showed cross-reactivity to AM4N (6.4% and 6.8%) and AM9 (2.6% and 3.6%) and testing on the Roche Integra 800 showed cross-reactivity to AM1c (2.4%), AM9 (10.7%), and AM19 (2.8%). Cyclosporine International Proficiency Testing Scheme samples, consisting of both pooled specimens from patients receiving CsA therapy as well as whole-blood specimens supplemented with CsA, were tested by the ARCHITECT assay at 6 sites and showed an average bias of -24 to -58 ng/mL versus LC/MSMS CsA and -2 to -37 ng/mL versus AxSYM CsA. Studies were performed with the ARCHITECT CsA assay on patient specimens with the following results: ARCHITECT CsA assay versus LC/MSMS, average bias of 31 ng/mL; ARCHITECT versus the Dade Dimension assay (4 sites), average biases of -7 to -228 ng/mL; ARCHITECT versus AxSYM and TDx, average biases of -4 and -53 ng/mL, respectively. Spearman correlation coefficients were >or=0.89. The ARCHITECT CsA assay has significantly reduced CsA metabolite interference relative to other immunoassays and is a convenient and sensitive semiautomated method to measure CsA in whole blood.

Comparison of three methods for cyclosporine therapeutic monitoring

Cyclosporine (CsA) is an immunosuppressive drug used extensively in human transplants of solid organs or bone marrow as well as in the treatment of autoimmune diseases. To optimize immunosuppressive efficacy and minimize adverse reactions, blood CsA concentrations are monitored to allow appropriate dosage adjustments. To establish objective criteria to compare various techniques of CsA monitoring, we performed a detailed study over 5 months to compare and evaluate three immunoassays methods in comparison to the reference method of high-performance liquid chromatography (HPLC). Our study included 976 samples that were evaluated by: the COBAS INTEGRA 800 (Roche Laboratories); the V-Twin (Dade Behring Laboratories); and the AxSYM FPIA (Abbott Laboratories). Our results showed that all of the immunoassays yielded slightly higher concentrations than HPLC. However CsA concentrations obtained by AxSYM were most close to those of HPLC, so that this method seemed to be more specific than the other two.

12-Hour Area Under the Curve Cyclosporine Concentrations Determined by a Validated Liquid Chromatography-Mass Spectrometry Procedure Compared With Fluorescence Polarization Immunoassay Reveals Sirolimus Effect on Cyclosporine Pharmacokinetics

Liquid chromatographic (LC) procedures have been applied to cyclosporine therapeutic drug monitoring (TDM) since the agent was introduced in 1983. In recent years, the advance to mass spectrometric (MS) detection has enhanced the capability of LC by providing more sensitive and selective detection, a wider analytical range, faster turnaround time, and relative ease of use. Although fluorescence polarization immunoassay (FPIA) is a widely popular technology for cyclosporine TDM, it is compromised by a limited analytical range and lack of selectivity for parent drug. Here, we present the validation of an LC-MS procedure that is equally applicable to use on single or tandem quadrupole instruments. An extensive method comparison with FPIA was performed using samples (n = 726) collected for full 12-hour pharmacokinetic studies on 121 renal transplant recipients. Patients were receiving either full-dose cyclosporine or primary sirolimus therapy complimented with low-dose cyclosporine. FPIA overestimated all cyclosporine concentrations to varying degrees depending on hour of collection (12 approximately 0 > 8 > 6 > 4 > 2-hour). The mean FPIA/LC-MS ratio was significantly higher at 0 hour in the presence of sirolimus (P = 0.008) and trended higher at the other collection times and for area under the curve. Sirolimus also had a significant effect on the FPIA/LC-MS ratio at 12 hour in studies with tmax at 2 hours (P = 0.042) but not 4 hours (P = 0.735). Use of LC-MS procedures for cyclosporine TDM provides for quantitation of approximately 20% more samples from patients receiving low-dose cyclosporine and reduces any errors in dosing that may occur because of the sirolimus effect on cyclosporine pharmacokinetics when combined with varying degrees of overestimation of cyclosporine concentrations by FPIA.

An up-date review on individualized dosage adjustment of calcineurin inhibitors in organ transplant patients

Calcineurin inhibitors, tacrolimus (FK506) and cyclosporine (ciclosporin A), are the primary immunosuppressive agents used on recipients of organ transplantations. The hepatic metabolism of these drugs by cytochrome P450 IIIA (CYP3A) subfamilies is considered a major eliminating process. The intestinal efflux-pump P-glycoprotein (Pgp) (multidrug resistance 1 [MDR1], ATP-binding cassette B1 [ABCB1]) and CYP3A4 have been demonstrated as important for the bioavailability of drugs, so called "absorptive barriers". Recently, an important role for CYP3A5 in the intestine for the oral clearance of drugs has been identified. Both tacrolimus and cyclosporine are substrates of Pgp, CYP3A4 and CYP3A5, and therefore, these molecules are potential pharmacokinetic factors with which to establish personalized dosage regimens for these drugs. Although the effect of single nucleotide polymorphisms in the MDR1/ABCB1 and CYP3A5 genes on the pharmacokinetics of immunosuppressant has been widely examined, some contradictions have been emerged. In living-donor liver transplant (LDLT) patients, the intestinal mRNA expression level of MDR1 and CYP3A5 genotyping both in the native intestine and in the grafted liver are suggested to be potential pharmacokinetic factors for adjusting initial dosage and predicting post-operative variation in the pharmacokinetics of tacrolimus. We review the pharmacokinetic and pharmacodynamic characteristics of these drugs including the large pharmacokinetic variation and potential individualized dosage adjustments based on the genomic information of transporters and metabolic enzymes as well as classical pharmacokinetic analyses based on therapeutic drug monitoring (TDM).

Evaluation of a novel semi-automated HPLC procedure for whole blood cyclosporin A confirms equivalence to adjusted monoclonal values from Abbott TDx

The problem in the measurement of cyclosporin (CyA) is that the widely used immuno-based assays suffer from interference by metabolites present in unpredictable excess. To resolve this, the consensus view has been to develop more specific and robust procedures for the measurement of CyA alone in order to give values similar to those obtained by HPLC. We developed an alternative strategy based on Abbott poly- and monoclonal assays to derive an adjusted monoclonal value as an equivalent measurement to HPLC. We have now evaluated a recently developed semi-automated HPLC procedure and used it to test the validity of the adjusted monoclonal value. The automated HPLC procedure with online clean-up was optimised for the separation of CyA and internal standard CyD. The assay was simple to use, precise and gave good recovery of cyclosporin from whole blood. Comparisons with the more specific immunoassays Abbott AxSym and EMIT showed close agreement, whereas Abbott monoclonal values indicated up to 20% positive bias. In contrast, the adjusted monoclonal values gave good agreement with HPLC. Data obtained from HPLC linked to tandem mass spectrometry (MS) indicated closer agreement with Abbott monoclonal values than expected, suggesting some positive bias with MS. The benefit of using an adjusted monoclonal value is that a result equivalent to HPLC is obtained, as well as an indication of the concentration of metabolites from the Abbott polyclonal measurement.

The potential replacement of HPLC by 125I-RIA for the characterization of cyclosporin A: a bioavailability study after oral administration in healthy human subjects

A significant overestimation of cyclosporin A (CsA) by a radioimmunoassay using 125I-labeled monoclonal antibody (125I-RIA), compared to the reference HPLC method, has been reported for a limited number of samples from transplant patients. However, the extent of the discrepancy, with respect to bioavailability parameters, has not been examined for the case of the oral administration of a single dose CsA to healthy subjects where a number of factors which might be involved in this overestimation (e.g. under steady state condition and a significant accumulation of CsA metabolites) would be absent. Therefore, the objective of this study was to assess the effect of potential difference manifested by the two analytical procedures, 125I-RIA and HPLC, on the bioavailability analysis of CsA. An oral CsA formulation was administered to 22 healthy male subjects and the blood samples were analysed by both 125I-RIA and HPLC. Significant discrepancies in the estimated CsA concentrations by the two methods (paired t-test, P < 0.001) were found. The difference (bias) increased with increasing concentrations of blood CsA (P < 0.001). However, despite the bias in CsA estimations, the AUC and Cmax, obtained by 125I-RIA and HPLC methods showed only small differences (i.e. 2% for AUC and 7% for Cmax). Thus, our results suggest that the bias of the 125I-RIA vis-a-vis the HPLC method in the estimation of CsA blood levels may not, in practice, affect the bioavailability analysis (e.g. bioequivalence study) of CsA in a situation where a single dose CsA is orally administered to healthy subjects.

Performance and Specificity of Monoclonal Immunoassays for Cyclosporine Monitoring: How Specific Is Specific?

Background: Immunoassays designed for the selective measurement of cyclosporin A (CsA) inadvertently show cross-reactivity for CsA metabolites. The extent and clinical significance of the resulting overestimation is controversial. A comprehensive assessment of old and new methods in clinical specimens is needed.

Methods: In a comprehensive evaluation, CsA was analyzed in 145 samples with the new CEDIA® assay and compared with the Emit® assay with the old and new pretreatments, the TDx® monoclonal and polyclonal assays, the AxSYM®, and HPLC. All samples were from patients with liver and/or kidney transplants.

Results: The CEDIA offered the easiest handling, followed by the AxSYM, which showed the longest calibration stability. The TDx monoclonal assay provided the lowest detection limit and the lowest CVs. The mean differences compared with HPLC were as follows: Emit, 9–12%; CEDIA, 18%; AxSYM, 29%; and TDx monoclonal, 57%. The CycloTrac® RIA paralleled the Emit results. In contrast to the mean differences, substantial (&gt;200%) and variable overestimations of the CsA concentration were observed in individual patient samples. Metabolic ratios, estimates of the overall concentrations of several cross-reacting metabolites (nonspecific TDx polyclonal/specific reference method), correlated with the apparent biases of the various monoclonal assays. Metabolic ratios varied up to 10-fold, which translated into biases for individual samples between −7% and +174%. The higher the cross-reactivity of an assay was, the higher was the range of biases observed. The interindividual differences markedly exceeded other factors of influence (organ transplanted, hepatic function).

Conclusion: Because assay bias cannot be predicted in individual samples, substantially erratic CsA dosing can result. The specificity of CsA assays for parent CsA remains a major concern.

Cyclosporin whole blood immunoassays (AxSYM, CEDIA, and Emit): a critical overview of performance characteristics and comparison with HPLC

Assays with different specificity are used for cyclosporin monitoring in clinical transplantation. A recent survey of 35 centers showed that 86% used immunoassays for cyclosporin A (CsA). In consensus documents the following performance criteria were recommended: (a) imprecision ≤10% at 50 μg/L and ≤5% at 300 μg/L; and (b) comparison with the reference method (HPLC) should yield a slope of 0.9–1.1, an intercept of −15 to 15 μg/L, and Sy‖x ≤15 μg/L. The newly developed CsA assays for the AxSYM (Abbott) and the CEDIATM (Boehringer Mannheim) as well as the EmitTM assay (Behring Diagnostica) were evaluated. Results from samples of heart, kidney, and liver recipients (100 specimens each) were compared with a validated HPLC-ultraviolet detection method. Between-series imprecision (CV) with commercial controls was 5.8% and 1.7% for AxSYM (70 and 300 μg/L), 11% and 5.5% for CEDIA (90 and 200 μg/L), and 8.1% and 4.5% for Emit (63 and 172 μg/L). In the presence of 300 μg/L parent CsA, cross-reactivities were (for AxSYM, CEDIA, and Emit, respectively) 7%, 4%, and none for AM1 (1 mg/L) and 12.6%, 25%, and 6% for AM9 (0.5 mg/L). Comparison with HPLC showed in heart and kidney recipients an average overestimation with the Emit and the CEDIA of ∼22%, with overestimation in the AxSYM of 32%. In liver recipients, the most challenging patient group, the CEDIA and the AxSYM showed a mean overestimation of 43% and 47%, respectively, and the Emit differed by 31% compared with HPLC. None of the immunoassays fully satisfied the performance criteria recommended in the consensus documents. In terms of specificity, Emit ranks before CEDIA, which ranks before AxSYM. Regarding imprecision, the ranking is AxSYM &lt; Emit &lt; CEDIA. These limitations must be considered when using these assays for therapeutic drug monitoring of CsA in clinical transplantation.

Microscale high-performance liquid chromatography-electrospray tandem mass spectrometry assay for cyclosporin A in blood

To facilitate quantitative analysis of cyclosporin A in low volume blood samples we developed a sensitive and specific microscale reversed-phase HPLC-electrospray tandem mass spectrometry assay. Blood samples (100 microl) were prepared by acetonitrile precipitation and C18 solid-phase extraction. Detection was by multiple-reactant monitoring. The method was linear over the range 5-1000 microg/l (r> or =0.997) with accuracy between 95.4 and 102.0% over this range. Total imprecision was 11.1% at 10 microg/l and 2.8% at 800 microg/l. Absolute recovery of cyclosporin A and internal standard was 72.5 and 73.3%, respectively. When this method was evaluated against a conventional HPLC with UV detection, in patient samples, they were interchangeable (y=0.988x + 10.0, r=0.996). This HPLC-ESI-MS-MS method will be applicable to therapeutic monitoring in paediatric transplant patients and multiple point pharmacokinetic studies in animals and humans.

Cyclosporin A trough levels correlate with serum lipoproteins and apolipoproteins: implications for therapeutic drug monitoring of cyclosporin A

In a prospective study over 6 months, the relationship between serum lipid parameters and CsA whole blood trough concentrations was investigated in 39 renal transplant recipients receiving a triple immunosuppressive therapy with cyclosporin (CsA), azathioprine and prednisone. CsA trough concentrations were measured with a selective monoclonal immunoassay (Abbott TDx). Six months after transplantation, significant positive correlations were observed between the CsA trough concentration and serum concentrations of triglycerides (r = 0.448, p < 0.01), total cholesterol (r = 0.360, p < 0.05), and apoB (r = 0.418, p < 0.01). After exclusion of patients with over hypertriglyceridemia (> 400 mg/dl), however, the associations were no longer significant. HDL-cholesterol (HDL-C) and apo AI concentrations showed significant inverse correlations with the CsA trough level (HDL-C: r = -0.427, p < 0.01; apoAI: r = -0.350, p < 0.05); the correlations with the CsA trough level were still significant (HDL-C: r = -0.379, p < 0.05; apoAI: r = -0.354, p < 0.05) after exclusion of patients with triglyceride levels of > 400 mg/dl. As a result of these divergent effects on the plasma lipids and lipoproteins, there was a strong positive association (r = 0.633, p < 0.001) between the CsA trough concentration and the total cholesterol/HDL-C ratio. Consequently, elevated total cholesterol/HDL-C ratios that represent an increased atherogenic risk tended to be associated with higher CsA trough levels. In monitoring CsA therapy of renal transplant recipients on maintenance immunosuppressive therapy, it may well be advisable to adjust CsA dosages to obtain CsA trough levels within the lower therapeutic range for patients with an unfavorably high TC/HDL-C ratio.

The EMIT Cyclosporine Assay: development of application protocols for the Boehringer Mannheim Hitachi 911 and 917 analyzers

OBJECTIVE

The purpose of this work was to develop applications for the EMIT Cyclosporine (CsA) Assay on the Hitachi 911 and 917 analyzers.

METHODS AND RESULTS

Instrument settings were optimized to arrive at the following assay characteristics on the Hitachi 917. Limit of sensitivity was 50 micrograms/L. Intra-assay coefficients of variation (CV) were 8.1% (n = 20; mean = 62 micrograms/L) and 4.2% (n = 20; mean = 315 micrograms/L), while interassay CVs were 13.0% (n = mean = 73 micrograms/L) and 5.7% (n = 43; mean = 391 micrograms/L). Recoveries of 95-104% were obtained by spiking aliquots of 3 whole blood patient pools of known CsA concentrations with CsA. Serial dilutions of 3 patient specimens demonstrated linear relationships between expected and actual CsA concentrations (r = 0.99, 0.99, 0.98; regression lines: y = 1.19x -17.1; y = 0.75x + 18.0; y = 1.01x + 3.7). Specimen carryover was not evident. Calibration stability is at least 10 days. Comparable assay characteristics were found for the Hitachi 911. Sequentially-collected trough whole blood specimens from renal (n = 3), liver (n = 3) and heart (n = 4) transplant patients prescribed CsA were collected up to 78 days post-transplant and analyzed by EMIT on the Hitachi 917 and also by fluorescence polarization immunoassay (FPIA) and high performance liquid chromatography (HPLC). The following linear regression equations were produced for the renal [EMIT = 0.801 (TDx) + 4.98, r = 0.91, Sy/x = 32, n = 37; EMIT = 0.877 (HPLC) + 56, r = 0.87, Sy/x = 38, n = 37]; liver [EMIT = 0.808 (TDx) - 27, r = 0.94, Sy/x = 42, n = 37; EMIT = 0.953 (HPLC) + 44, r = 0.89, Sy/x = 57, n = 37] and heart [EMIT = 0.820 (TDx) - 24, r = 0.94, Sy/x = 31, n = 45, EMIT = 0.956 (HPLC) + 54, r = 0.91, Sy/x = 38, n = 45] patient samples. FPIA values average 32% more than EMIT-derived CsA concentrations on the Hitachi 917, which in turn averaged 15% more than HPLC values. In addition, these levels were compared intra-individually. CsA concentrations within all patients were significantly higher (p < 0.05, paired t-test) by FPIA compared to EMIT and by FPIA compared to HPLC. Although CsA concentrations within most patients were significantly higher (p < 0.05) by EMIT compared to HPLC, levels determined in 4 transplant patients (1 renal, 1 liver, 2 heart) were not different.

CONCLUSION

Development of applications for the EMIT CsA Assay on two highly automated, random access instruments, the Hitachi 911 and Hitachi 917, enhances the versatility of the immunoassay for routine therapeutic drug monitoring of this immunosuppressant in the clinical setting.

Simultaneous quantification of cyclosporin A and its major metabolites by time‐of‐flight secondary‐ion mass spectrometry and matrix‐assisted laser desorption/ionization mass spectrometry utilizing data analysis techniques: Comparison with high‐performance liquid chromatography

Simultaneous quantification of cyclosporin A (CsA) and its major metabolite (AM1) in blood has been achieved using time‐of‐flight secondary‐ion mass spectrometry (TOF‐SIMS) and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI/TOF‐MS). Previous investigations indicated that spectral interferences exist in the analysis of CsA blood samples by the above methods. In TOF‐SIMS, interference is caused by overlap of the Ag‐cationized internal standard, cyclosporin D (CsD), with the Ag‐cationized metabolite, AM1. To resolve this interference and obtain quantitative information, cross‐correlation analysis was applied to the TOF‐SIMS data. Application of damped non‐linear least squares curve‐fitting was carried out to resolve an interference in the MALDI/TOF‐MS data due to multiple cationization products (i.e. Na and K). Measurement of standard samples indicates that the minimum accuracy (95% confidence level) of the TOF‐SIMS method was better than 9% for CsA and 13% for AM1 using only one standard curve'. Similarly, the minimum accuracy of the MALDI/TOF‐MS method was determined to be 14% for CsA and better than 25% for AM1. Blood samples obtained from transplant patients receiving CsA were analyzed by polyclonal fluorescence polarization immunoassay, high‐performance liquid chromatography (HPLC), and by both TOF‐MS methods. Both TOF‐MS results for CsA and mono‐hydroxylated CsA are in good agreement with the HPLC results.

Analysis of whole-blood cyclosporin G by liquid chromatography in renal transplant recipients

Cyclosporin G (CsG) is less nephrotoxic than Cyclosporin A (CsA) and is undergoing clinical trials for use as an immunosuppressive agent after renal transplantation. In this study, CsG was measured by a rapid high-performance liquid chromatography (HPLC) technique in blood samples (n = 107) received from renal transplant recipients. The HPLC assay proved to be analytically suitable in that it was sensitive, linear, and precise and had high recovery (102%). However, interference was observed from some potentially co-administered drugs such as calcitriol, ferrous sulfate, hydrazaline, and minoxidil. The HPLC assay for CsG correlated well with a FPIA (Abbott TDx), FPIA = 0.964 (HPLC) + 33.59, r = 0.9819, Sy/x = 36.66 for patients receiving a low dose of CsG (5 mg/kg/day) and a high dose (10 mg/kg/day). Furthermore, the HPLC technique was capable of measuring predictable CsG concentrations when the drug was tapered to lower doses at various stages of the 16 week clinical trial. The HPLC for CsG has the further advantage that the same system and mobile phase can be used to measure CsA while using CsC as the interval standard.

EMIT cyclosporine assay: development of an application protocol for Technicon AXON System

Monitoring parent drug cyclosporine (CsA) concentrations in whole blood has been facilitated by the introduction of automated nonisotopic immunoassays [fluorescence polarization monoclonal whole blood assay (FPIA), EMIT Cyclosporine Assay]. The latter assay currently has a defined application only for Cobas Mira Chemistry Systems. The purpose of our work was to develop an application for this assay on the Technicon AXON. Instrument settings were optimized to arrive at the following assay performance characteristics. Limit of sensitivity was 50 micrograms/L. Interassay coefficients of variation (CV) were 11.2% (n = 16; mean = 81 micrograms/L) and 9.4% (n = 16; mean = 418 micrograms/L). Recoveries of 102, 112, and 117% were obtained by spiking aliquots of 10 whole blood patient pools of known CsA concentrations with 50, 100, and 200 micrograms/L CsA, respectively. Serial dilutions of two patient specimens demonstrated a linear relationship between expected and actual CsA concentrations (r = 0.996, 0.998; regression lines; y = 0.989x + 11.7; y = 0.979x + 9.5). Carryover and interference (lipemia) were not evident. Instrument calibration stability is at least 1 month. Comparison with CsA concentrations analyzed in renal transplant patients by the FPIA assay produced a linear regression equation of EMIT = 1.113x - 44.5, r = 0.968, Sy/x = 20.8, n = 32. Comparison with high-performance liquid chromatography (HPLC)-derived values in the same patient population produced a linear regression equation of EMIT = 1.114x - 16.4, r = 0.970, Sy/x = 20.2. FPIA-derived CsA concentrations averaged 14.2% more than those obtained with the EMIT method with the latter averaging 1.3% more than HPLC values.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of cyclosporine assays using sequential samples from selected transplant patients

The monitoring of cyclosporine (CsA) whole blood concentrations is an integral part of immunosuppressive treatment with this drug. Although such monitoring has been facilitated by the introduction of monoclonal immunoassay techniques, there is a paucity of published data comparing the assays longitudinally in selected patients. The purpose of our study was to co-evaluate two monoclonal immunoassays (Cyclosporine FPIA whole blood assay, Abbott Laboratories; Cyclo-Trac SP-whole blood RIA, Incstar Inc.) and a high-performance liquid chromatography (HPLC) technique for quantitating CsA in sequentially collected trough whole blood samples from 14 patients up to 75 days after renal (n = 6), heart (n = 3), and liver (n = 5) transplantation. HPLC CsA metabolite analyses (AM1, AM9, AM4N) were performed. Although CsA concentrations within most patients were significantly higher (p < 0.05, paired t test) when measured by both immunoassay techniques compared to HPLC, levels determined in three patients, (one liver, two renal) for the FPIA/HPLC comparison and one patient (liver) for the RIA/HPLC comparison were not significantly different (p > 0.05). CsA levels within nine patients were not significantly different (p > 0.05) when FPIA and RIA were compared, but results within three patients, (one liver, two renal) were significantly higher (p < 0.05) by RIA compared to FPIA, but results within one patient (heart) were significantly higher (p < 0.05) by FPIA. Our results demonstrate first that depending on the patient, HPLC-derived CsA results are not consistently lower than results generated by immunoassay techniques and second that CsA levels obtained by FPIA are statistically equivalent or in some patients, statistically less than RIA-derived levels.