Differences in the variability of cerebral proton magnetic resonance spectroscopy (1H-MRS) measurements within three HIV-infected cohorts.
BACKGROUND
Cerebral functional impairment remains prevalent in effectively treated HIV-infected subjects. As the results of formal cognitive testing are highly variable, surrogate markers to accurately measure cerebral function parameters are needed. Such markers include measurement of cerebral metabolite ratios (CMR) using proton magnetic resonance spectroscopy (1H-MRS). However, data on the inter-subject variability of CMR are sparse. Our aim was to assess inter-subject variability in CMRs within three different HIV-infected cohorts.


METHODS
Cerebral 1H-MRS was performed using a Phillips Achieva™ 1.5 Tesla magnetic resonance scanner in HIV-infected subjects as follows: 12 subjects before (group 1) and after intensification of antiretroviral therapy with maraviroc (group 2) and 13 subjects with acute viral hepatitis C (HCV) co-infection (group 3). The coefficients of variation (CV) for CMRs in each group were determined and compared using non-parametric tests to determine whether the inter-subject variability differed significantly. All baseline characteristics between the groups were similar.


RESULTS
Overall CVs for all CMRs in groups 1, 2 and 3 were 32.3%, 33.2% and 23.4%, respectively (group 1 vs. 2, p=0.863; group 1 vs. 3, p=0.076). On testing for differences in variability between individual CMRs, two metabolites in the right basal ganglia (RBG) had statistically significantly different CVs when comparing group 1 with group 3: N-acetyl aspartate/creatine (NAA/Cr), p=0.029 and myo-Inositol/creatine (mI/Cr), p=0.016.


CONCLUSIONS
The variability of 1H MRS-measurable CMRs in HIV-infected individuals was lower in those with acute HCV co-infection (group 3).We can conclude that the use of these CMRs in 1H MRS imaging in patients with HIV/acute HCV co-infection is more reliable to assess cerebral function than in patients with HIV infection alone. This has implications for future sample size estimations.
Imperial College London, London, UK shivanee.vigneswaran@nhs.net.
Shivanee
S
Vigneswaran
Division of medicine, Brighton and Sussex Medical School Department of HIV and GU Medicine, Imperial College Healthcare NHS Trust, London, UK.
Jaime H Vera
JH
Rojas
Department of HIV and GU Medicine, Imperial College Healthcare NHS Trust, London, UK.
Lucy
L
Garvey
Department of Medicine, Faculty of Medicine, Imperial College London, St Mary's Hospital Campus, London, UK.
Simon
S
Taylor-Robinson
Department of HIV and GU Medicine, Imperial College Healthcare NHS Trust, London, UK.
Alan
A
Winston
D000328:Adult; D023241:Antiretroviral Therapy, Highly Active; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001479:Basal Ganglia / Q000737:chemistry / Q000378:metabolism / Q000473:pathology; D001921:Brain / Q000473:pathology; D001923:Brain Chemistry; D015331:Cohort Studies; D003401:Creatine / Q000378:metabolism; D003510:Cyclohexanes / Q000493:pharmacokinetics / Q000627:therapeutic use; D005260:Female; D023581:HIV Fusion Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D015658:HIV Infections / Q000150:complications / Q000188:drug therapy / Q000378:metabolism*; D006526:Hepatitis C / Q000150:complications / Q000188:drug therapy / Q000378:metabolism; D006801:Humans; D007294:Inositol / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D008297:Male; D000077592:Maraviroc; D008875:Middle Aged; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D011522:Protons; D014230:Triazoles / Q000493:pharmacokinetics / Q000627:therapeutic use; D055815:Young Adult
D003510:Cyclohexanes; D023581:HIV Fusion Inhibitors; D011522:Protons; D014230:Triazoles; D001224:Aspartic Acid; D007294:Inositol; C000179:N-acetylaspartate; D000077592:Maraviroc; D003401:Creatine
1H MRS; HIV; acute HCV; co-infection; variability