INTRODUCTION: Tenofovir disoproxil fumarate (TDF) -containing regimens have been 
associated with nephrotoxicity and hypophosphatemia in HIV-infected patients. 
The objective of this study was to assess the possible risk factors for 
hypophosphatemia and evaluate the relationship between fractional excretion of 
filtered phosphate (FePi) and hypophosphatemia in TDF users.
PATIENT AND METHODS: Patients were enrolled in a prospective cohort study 
between January 2011 and December 2014. We classified experienced HIV-infected 
patients (individuals maintained on antiretroviral therapy (ART) for 6 months or 
more) and naïve patients into 3 treatment groups: TDF-containing ART (group 1), 
non-TDF-containing ART (never received TDF or had not received TDF in the past 6 
months; group 2) and naive to antiretroviral therapy (group 3). Specimens from 
each individual were assessed for serum phosphate, serum creatinine, urine 
phosphate, and urine creatinine. Multivariable logistic regression was performed 
to control for the following variables measured at baseline: eGFR, age, sex, 
sexual orientation, injection drug use (IDUs), HIV-RNA viral load, and CD4 cell 
count.
RESULTS: The frequency of hypophosphatemia in groups 1, 2, and 3 was 20.2%, 
7.2%, and 14.6%, respectively (P = 0.002). FePi above 10% also was significantly 
associated with hypophosphatemia (P = 0.003; adjusted odds ratio = 2.54). 
Patients with elevated CD4 cell counts (>500 cells/μL) exhibited a lower risk of 
hypophosphatemia (P = 0.002; adjusted odds ratio = 0.35).
CONCLUSIONS: Hypophosphatemia is a multifactorial etiology; FePi was confirmed 
as a suggested method to predict the risk of hypophosphatemia in TDF users. 
Clinical Trial Number: TYGH103011.