Analytical evaluation of a new immunonephelometric method for homocysteine measurement.
OBJECTIVE
Increased plasma homocysteine, a sulphur amino acid closely related to methionine metabolism, is considered an independent risk factor for cardiovascular diseases. Over the last years, the request to clinical laboratories for homocysteine measurement is constantly increased and, for this reason, several new methods have been developed, mainly with the aim of using them on completely automated instruments for routine analyses. In this paper, we evaluated a new immunonephelometric method for homocysteine determination on the Dade Behring BNII nephelometer.


METHODS
Linearity, recovery, limit of detection (LOD) and total imprecision and were assessed; moreover, the method was compared with a HPLC reference method and with an automated immunoassay method (AxSYM Abbott).


RESULTS
Recovery range was 96.4-104.2%, LOD was 0.5 micromol/L and total imprecision ranged from 5.0% to 7.6%. For the comparison study, the immunonephelometric method showed a good correlation both with HPLC (Y=1.02X-0.79, R(2)=0.99) and with the AxSYM method (Y=1.003X+0.06, R(2)=0.98). The Bland-Altman plot analysis shows that the immunonephelometric method has a slight positive bias with both HPLC (mean: 1.03 micromol/L, 95% confidence interval: 0.28-1.79 micromol/L) and AxSYM methods (mean: 0.45 micromol/L, 95% confidence interval: -0.03-0.94 micromol/L).


CONCLUSIONS
The new nephelometric method from Dade Behring, for its analytical performance, can be easily considered a suitable method for homocysteine routine measurement; moreover, it cannot be ruled out that the widespread availability of nephelometers in clinical laboratories play a leading role in the choice of this method.
Zappacosta
Bruno
B
Centro di Ricerca e Formazione ad Alta Tecnologia nelle Scienze Biomediche, Università Cattolica del Sacro Cuore, Contrada Tappino 86100 Campobasso, Italy. bzappacosta@rm.unicatt.it
Persichilli
Silvia
S
Minucci
Angelo
A
Scribano
Donata
D
Antenucci
Mirca
M
Fasanella
Silvia
S
Neri
Paola
P
Giardina
Bruno
B
De Sole
Pasquale
P
D043383:Adenosylhomocysteinase / Q000378:metabolism; D000328:Adult; D000368:Aged; D002851:Chromatography, High Pressure Liquid; D004229:Dithiothreitol / Q000378:metabolism; D005260:Female; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D007118:Immunoassay / Q000379:methods; D008297:Male; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry / Q000295:instrumentation / Q000379:methods; D015203:Reproducibility of Results; D012435:S-Adenosylhomocysteine / Q000378:metabolism; D013954:Thyroglobulin / Q000378:metabolism
D006710:Homocysteine; D013954:Thyroglobulin; D012435:S-Adenosylhomocysteine; D043383:Adenosylhomocysteinase; D004229:Dithiothreitol