Hyperhomocysteinemia: could the post-methionine oral loading test sometimes be avoided?
OBJECTIVE
Measurement of homocysteinemia, a risk factor for venous and arterial thrombosis, is carried out in patients fasting for 12 hours and after an oral methionine load (PML). The procedure is time-consuming and several of the patients suffer from nausea and malaise. We wondered whether methionine loading could sometimes be avoided by considering fasting homocysteinemia (tHcy) levels.


METHODS
We evaluated whether fasting tHcy levels were useful to predict PML and deltaPML tHcy with acceptable sensitivity and specificity in 381 patients with venous and arterial thrombosis through the generation of receiver operating characteristic curves.


RESULTS
Both PML and deltaPML tHcy correlated with fasting tHcy values. The cut-off of fasting tHcy value yielding a 100% sensitivity in predicting normal PML and deltaPML tHcy was 6.5 and 5.0 micromol/L in females, and 7.1 and 7.2 micromol/L in males. Fasting tHcy values yielding a 95% specificity in predicting a positive PML and tHcy result ranged from 12.5 to 13.1 micromol/L in males and from 10.4 to 10.5 micromol/L in females. A 95% specificity in predicting a positive deltaPML tHcy result ranged from 10.8 to 11.6 micromol/L in females and from 15.9 to 17.0 micromol/L in men. Considering PML tHcy, 186 out of 381 patients could have avoided methionine loading while using deltaPML tHcy 123 out of 381 could have done so.


CONCLUSIONS
Nearly 50% of our patients considering PML tHcy, and about 30% considering deltaPML tHcy could have been spared the methionine loading test. We propose this model for those who wish to carry out this analysis on their own.
Marongiu
Francesco
F
Dipartimento di Scienze Mediche Internistiche, University of Cagliari, Italy. marongiu@pacs.unica.it
Fenu
Lara
L
Pisu
Giulia
G
Contu
Paolo
P
Barcellona
Doris
D
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005215:Fasting; D005260:Female; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D020138:Hyperhomocysteinemia / Q000175:diagnosis*; D008297:Male; D008715:Methionine / Q000008:administration & dosage / Q000009:adverse effects; D008875:Middle Aged; D012680:Sensitivity and Specificity; D013927:Thrombosis / Q000097:blood
D006710:Homocysteine; D008715:Methionine