TY - JOUR
T1 - Possible false-negative results on therapeutic drug monitoring of phenytoin using a particle enhanced turbidimetric inhibition immunoassay in a patient with a high level of IgM
AU - Hirata, Kenshiro
AU - Saruwatari, Junji
AU - Enoki, Yuhuki
AU - Iwata, Kazufumi
AU - Urata, Yukino
AU - Aizawa, Keiji
AU - Ueda, Kentaro
AU - Shirouzono, Takumi
AU - Imamura, Motoki
AU - Moriuchi, Hiroshi
AU - Ishima, Yu
AU - Kadowaki, Daisuke
AU - Watanabe, Hiroshi
AU - Hirata, Sumio
AU - Maruyama, Toru
AU - Fukunaga, Eiko
PY - 2014/10/12
Y1 - 2014/10/12
N2 - In this report, the authors described the unusual case of a patient in whom the plasma phenytoin concentration was unexpectedly not detected on a particle-enhanced turbidimetric inhibition immunoassay (PETINIA) technique, a typical immunoassay for phenytoin. The plasma concentration was measured using PETINIA and high-performance liquid chromatography in a 69-year-old male patient treated with fosphenytoin intravenously at the standard dose for 7 days. Although the plasma concentration of phenytoin was below the limit of detection (<0.5 mcg/mL) on PETINIA after the administration of fosphenytoin, the trough plasma concentration was estimated to be between 5 and 10 mg/L on high-performance liquid chromatography. When the plasma concentrations of IgM and IgG were measured using an enzyme-linked immunosorbent assay, the plasma IgG level was within the reference range, whereas the plasma IgM level was 2-3 times higher than the upper limit of the reference range. We concluded that the PETINIA method yielded a possible false-negative result regarding the phenytoin level in this patient, perhaps because of some hindrance to the measurement process by IgM. This case suggests that false-negative results should be considered when therapeutic drug monitoring reveals abnormally low values using PETINIA and that it is necessary to evaluate the plasma IgM level.
AB - In this report, the authors described the unusual case of a patient in whom the plasma phenytoin concentration was unexpectedly not detected on a particle-enhanced turbidimetric inhibition immunoassay (PETINIA) technique, a typical immunoassay for phenytoin. The plasma concentration was measured using PETINIA and high-performance liquid chromatography in a 69-year-old male patient treated with fosphenytoin intravenously at the standard dose for 7 days. Although the plasma concentration of phenytoin was below the limit of detection (<0.5 mcg/mL) on PETINIA after the administration of fosphenytoin, the trough plasma concentration was estimated to be between 5 and 10 mg/L on high-performance liquid chromatography. When the plasma concentrations of IgM and IgG were measured using an enzyme-linked immunosorbent assay, the plasma IgG level was within the reference range, whereas the plasma IgM level was 2-3 times higher than the upper limit of the reference range. We concluded that the PETINIA method yielded a possible false-negative result regarding the phenytoin level in this patient, perhaps because of some hindrance to the measurement process by IgM. This case suggests that false-negative results should be considered when therapeutic drug monitoring reveals abnormally low values using PETINIA and that it is necessary to evaluate the plasma IgM level.
KW - IgM
KW - false-negative
KW - particle-enhanced turbidimetric inhibition immunoassay
KW - phenytoin
KW - therapeutic drug monitoring
UR - http://www.scopus.com/inward/record.url?scp=84930178993&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84930178993&partnerID=8YFLogxK
U2 - 10.1097/FTD.0000000000000067
DO - 10.1097/FTD.0000000000000067
M3 - Article
C2 - 24632808
AN - SCOPUS:84930178993
VL - 36
SP - 553
EP - 555
JO - Therapeutic Drug Monitoring
JF - Therapeutic Drug Monitoring
SN - 0163-4356
IS - 5
ER -