A Comparison of the Immunochemical Methods, PETINIA and EMIT, With That of HPLC-UV for the Routine Monitoring of Mycophenolic Acid in Heart Transplant Patients.
BACKGROUND
The aim of this study was to evaluate particle enhanced turbidimetric inhibition immunoassay (PETINIA) recently developed for mycophenolic acid (MPA) determination in plasma and to compare it with a reference high-performance liquid chromatography (HPLC) method, using samples from heart transplant recipients. The results are presented in the context of PETINIA being compared with enzyme multiplied immunoassay technique (EMIT).


METHODS
PETINIA evaluation was performed using 194 routine trough plasma samples at steady state. EMIT was evaluated using 677 samples from 61 steady-state 12-hour profiles obtained from 35 heart transplant patients. Evaluation was undertaken on a Dimension EXL 200 analyzer (PETINIA) and on a Viva-E analyzer (EMIT).


RESULTS
The mean MPA concentration measured by PETINIA was significantly higher than that measured by high-performance liquid chromatography combined with UV detector (2.36 ± 1.30 mcg/mL versus 1.82 ± 1.23 mcg/mL, respectively, P < 0.0001). Bland-Altman analysis revealed a mean bias of 0.54 mcg/mL [95% confidence interval (CI), 0.49-0.59] comprising 33.48% (95% CI, 30.34-36.61). Passing-Bablok regression was: y = 1.100x + 0.38 (95% CI for slope: 1.044-1.154 and for intercept: 0.30-0.47). Regardless of a significant observed correlation (r = 0.9230, P < 0.0001), the statistical analyses showed a significant difference between PETINIA and the reference chromatographic method. The mean MPA concentration measured by EMIT was significantly higher than that measured by HPLC (7.48 ± 8.34 mcg/mL versus 5.57 ± 6.61 mcg/mL, respectively, P < 0.0001) with a mean bias of 1.91 mcg/mL (95% CI, 1.75-2.07) comprising 35.91% (95% CI, 34.37-37.45). The significant difference between EMIT and HPLC was confirmed by Passing-Bablok regression: y = 1.300x + 0.24 (95% CI for slope: 1.279-1.324 and for intercept: 0.18-0.29). The analysis of the determinations, grouped by sampling time, revealed positive bias between EMIT and HPLC ranging from 24.54% to 42.77% and inversely proportional to MPA concentrations with r = 0.9122 (P < 0.001).


CONCLUSIONS
The new immunochemical PETINIA method was associated with significantly higher MPA concentrations in routine therapeutic drug monitoring samples from heart transplant patients. The magnitude of the MPA overestimation was similar to that observed by use of the EMIT method.
*Clinical Pharmacology Unit, Department of Clinical Biochemistry, Institute of Cardiology; and †Department of Drug Chemistry, Faculty of Pharmacy, Medical University of Warsaw, Poland.
Paweł K
PK
Kunicki
Tomasz
T
Pawiński
Aleksandra
A
Boczek
Joanna
J
Waś
Magdalena
M
Bodnar-Broniarczyk
D000293:Adolescent; D000328:Adult; D000368:Aged; D002851:Chromatography, High Pressure Liquid; D016903:Drug Monitoring / Q000379:methods*; D017248:Enzyme Multiplied Immunoassay Technique; D005260:Female; D016027:Heart Transplantation; D006801:Humans; D007166:Immunosuppressive Agents / Q000097:blood; D008297:Male; D008875:Middle Aged; D009173:Mycophenolic Acid / Q000097:blood*; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D013056:Spectrophotometry, Ultraviolet; D055815:Young Adult
D007166:Immunosuppressive Agents; D009173:Mycophenolic Acid