The Change Of Serum Phosphorus In Chronic Hepatitis B Patients During Long-term Adefovir Dipivoxil Treatment

Objective: Antiviral treatment is the basal therapy for patients withhepatitis B virus (HBV) infection to reduce HBV replication. Adefovirdipivoxil (ADV) is one of nucleotide analogs wich has been used for antiviraltherapy. The adverse reaction of long-term administration of ADV has beenreported recently, we should pay attention to the safety of ADV, the mainadverse event is renal toxicity wich is usually in form of high serum creatinineor hypophosphatemia. The aim of this study was to determine the incidenceand factors associated with hypophosphatemia in patients with HBV infectionon long-term treatment with ADV. The aim of our work was to assess theassociation between frequency of genotype distribution of rs6420094andrs4074995and serum phosphorus too. Bone mineral density (BMD) wasdetermined in some patients who had developed hypophosphatemia toinvestigate the incidence and factors associated with abnormal BMD wichcomprises osteopenia and osteoporosis.Methods:198Chinese patients who were treated with ADV (10mg/d)more than2years were enrolled in our study, the clinical data of these patientswere collected. Patients were divided into hypophosphatemia group andnormal serum phosphorus group to determine the incidence ofhypophosphatemia. The factors associated with hypophosphatemia in bothgroup were analyzed by single and muti-factor logistic regression. Relativefactors in our study were listed as bellow: sex, age, weight, the time of therapy,diagnosis, treatment.3ml of venous blood from each of31patients withhypophosphatemia and60patients with normal serum phosphorus wascollected. rs6420094and rs4074995were genotyped by polymerase chainreaction-restrictive fragment length polymorphism (PCR-RFLP) analysis. Weinvestigated the relationship between genotype and serum phosphorus concentration. BMD were examined in28patients who had developedhypophosphatemia, these patients were divided into normal BMD group andabnormal BMD group, so as to determine the incidence of abnormal BMD.The factors associated with abnormal BMD in both group were analyzed byFisher s exact test and muti-factor logistic regression. Relative factors inour study were listed as bellow: sex, age, weight, the time of therapy, serumphospharus, diagnosis, treatment, genotype.Statistical analysis was performed by SPSS17.0software package.Clinical data were analyzed by single and muti-factor logistic regression. Theodds ratio and95%confidence interval were calculated by an unconditionallogistic regression model, the exclusion and inclusion criteria were0.1and0.05. Ratio was compared by Pearson Chi-Square test or Fisher s exact testin the case of P≈a or n<40. All the tests are two-side test, P<0.05wasconsidered as statistical difference. Hardy-Weinberg analysis and linkagedisequilibrium coefficient were performed by SHEsis software package,r2>0.33and D’>0.7were considered as linkage disequilibrium.Results:155(27.8%) of the198patients who were with HBV infection onlong-term treatment with ADV developed hypophosphatemia. Longer courseof treatment and older age were identified as significant determinants ofADV-induced hypophosphatemia by multivariate analysis, the odds ratios and95%confidence intervals were1.316(1.000~1.730) and1.458(1.083~1.963)respectively.2The rs6420094and rs4074995genotypes were compatible with thoseexpected from Hardy-Weinberg equilibrium, the P value were0.167,0.572,0.316,0.856. rs6420094and rs4074995were in linkage disequilibrium(D=0.759, r2=0.412). The number of rs407499of hypophosphatemia groupA/A was2, A/G was11, G/G was18; the number of rs407499of normolgroup A/A was1, A/G was21, G/G was38. There was no difference in allelefrequency distribution of the rs4074995between hypophosphatemia group andnormol group (P=0.429). The number of rs6420094of hypophosphatemia group A/A was13, A/G was13, G/G was5; the number of rs6420094ofnormol group A/A was35, A/G was24, G/G was1. The allele A frequency ofrs6420094of normol group (78.3%) was higher than the hypophosphatemiagroup (62.9%), P=0.026.317(60.7%) of the28patients who had hypophosphatemia developedabnormal BMD, the cases of osteopenia and osteoporosis were10and7respectively. The level of hypophosphatemia was statistically differentbetween abnormal BMD group and normal BMD group (P=0.041), otherfactors were not substantially different between the two groups.Conclusion:1The incidence of hypophosphatemia is27.8%in patients with HBVinfection on long-term treatment with ADV. Older age and the longer term oftreatment are independent risk factors related with hypophosphatemia.2The allele frequency of rs6420094is closely related to serumphosphorus concentration of patients with HBV infection on long-termtreatment with ADV, the frequency of allele A of normol group is higher thanthe hypophosphatemia group. There is no association between allele frequencyof rs4074995and serum phosphorus concentration.3The incidence of abnormal BMD is60.7%in patients who hasdeveloped hypophosphatemia, the lower serum phosphorus is an independentrisk factor related with the abnormal BMD.4PCR-RFLP analysis is accurate and inexpensive. If there is no incisionenzyme or there is an expensive incision enzyme, one or more mismatch basescan be used in a primer to create a restriction site by combining SNP site afterPCR. If the efficiency of amplification is low or there is non-specificamplification, the semi-nested PCR can be considered to be applied.