Sickle Cell Disease Proteinuria Is Not Associated With Systolic Blood Pressure, CSSCD-Defined Hypertension, or Family History Of Hypertension In An International Cohort Of SCD Patients

The prevalence of renal disease in sickle cell disease (SCD) is strikingly high and is associated with morbidity and mortality (Becker et al 2010, Powars et al 2005). In SCD children there is initially hyperfiltration with high GFRs followed by increasing proteinuria in the adolescent and adult SCD pts. (Becker at al 2010). Historically, hypertension (HTN) has been associated with Renal Disease in the general population and a few adult sickle cell nephropathy studies. HTN has been associated with Stroke in SCD. In an ongoing multicenter, international Renal SCD Cohort Study, we investigated the association Microalbuminuria and Macroalbuminuria to Patients Blood Pressure (SBP and DBP), Hypertension based on CSSCD Group Age Defined BP for SCD patients >90%tile (Pegelow et al 1997), and Family history (FH) of Hypertension and Renal Disease in a Crossectional (Peds and Adults), International, Multicenter group of SCD patients.

272 pediatric and adult SCD (3-59 y/o) patients were recruited at baseline from 6 Centers (USA: Univ of Michigan, Case Medical Center/Rainbow Babies, Albert Einstein-Montefiore Medical Center, Univ of Connecticut; Italy: Univ. of Padova, Univ of Naples; Ghana: Korle-Bu Teaching Hospital). 88%(N=236) were severe SCD (SSorSBeta Zero) and 12%(N=31) were Mild Phenotype (SC or SBetaPlus). 58% were Children (<18y/o) and 42%(>18y/o) adults. FH of HTN and Renal Disease were obtained in 1^st and 2^nddegree relatives. Clinical history and laboratory studies including Pain crises patterns, SBP, DBP, BMI, CBC, Serum Crt, were collected. We obtained Urine Microalbumin/Crt(UMA) (mg/gm) obtained in 169 patients and categorized patients into 1) No Microalbuminuria(No UMA)<30mg/gm, 2) Microalbuminuria(MicroUMA) 30-299mg/gm and 3) Macroalbuminuria (MacroUMA) and obtained Urine protein/crt gm/gm(UProtCrt) in 101 SCD pts and were categorized 1) No proteinuria(NoUProt) <0.2 and 2) Macroproteinuria(MacroUProt)>0.2. Patient’s HTN was defined based on CSSCD SBP or DBP> 90%tile for each specifically defined age group( Pegelow et al 1997).

In our SCD Renal Cohort Study, NoUMA in 71%(110/169), MicroUMA in 29%(48/169), MacroUMA in 2.2%(6/169) were observed. We also found NoUProt in 75%(N=75) and MacroUProt in 25%(n=25) within our cohort. Severe SCD pts represented 96%(n=46) of the MicroUMA pts, 100% or MacroUMA pts(N=6), and 92% MacroUProt pts(N=23). Proteinuria was disproportionately represented within the Adult SCD pts : 50% of Adults with MicroUMA(n=31) while only 16%(n=17) of Peds. UMA Mean Adult levels was 102(mean) vs. Peds UMA levels of 22(mean),(p=0.009); Also, Adult UProtCrt=0.21(mean)levels were >Peds=0.16, (p<0.001). HTN defined as SBP>90%tile or DBP >90%tile was present in 30%of the subjects(n=77).Thirty-One Percent(n=32) of Adults and 30%(n=45) of Peds pts had HTN. In a Bivariate Analysis(Pearson’s Correlation), HTN was not associated with UMA levels(p=0.919) or UPrtCrt levels(p=0.330). Further, mean UMA was lower in HTN SCD pts( m=24) vs NonHTN(SBP) pts(m=51). Mean UProt levels lower in the HTN group(0.15 ) vs NonHTN(0.20). SBP alone was not associated with UMA( p=0.083), UPrt( p=0.804) levels, MicroUMA(p=0.596). While FH of HTN was common in 75% of pts, FH HTN was not associated with UMA and UProtCrt levels, MicroUMA, MacroUMA, MacroUProt( p>0.05) patients. FH of Renal Disease was not associated with Proteinuria within our Cohort. However, Age( p<0.001: UProtCrt levels, UMA levels, MicroUMA, SBP) and hemoglobin(p=0.034: UProt Crt levels) was significantly associated with proteinuria within our cohort based on Bivariate Analysis. BMI was associated with SBP(p<0.001) and DBP(p<0.001) but not UProt or UMA levels. Further analysis revealed increasing proteinuria(UMA) within aging SCD pts:( 6-10 UMA= 15, 11-19 UMA =42, >20y/o UMA=114)(p=.035 One Way Anova)

Systolic Blood Pressure, HTN defined as SBP>90%tile or DBP >90%tile from the CSSCD Group, FH of HTN was not associated with Micro or Macroproteinuria based on UProtCrt and UMA levels in an international, cross-sectional cohort of SCD patients. Hemoglobin level and older age were strongly associated with proteinuria within our cohort of patients, consistent with previously well established studies. These findings are supportive of other factors outside of HTN including those intrinsic to SCD contributing to early onset SCD nephropathy.

Perrotta:Novartis: Research Funding.