Abstract Body (Do not enter title and authors here): Background: Patients with chronic kidney disease (CKD) encounter with chronic inflammatory state; however, the magnitude of the association between high-sensitivity C-reactive protein (CRP) and the severity of CKD among those other inflammatory diseases such as hypertension (HTN) and obesity is unknown. We aim to examine the association between CRP and CKD stage in patients with varying HTN and obesity statuses.

Method: A retrospective cross-sectional study utilizing data from the 2017 - 2020 NHANES included participants with available CRP. The association between the quartile (Q) of CRP and CKD stages (stages 1, 2, 3a, 3b, 4, and 5) stratified by self-reported HTN and obesity status defined by BMI of < or >/= 30 kg/m² were examined by multiple ordered logistic regression analyses.

Results: Of 9,693 adult participants, the mean age+/-SD was 50±19 years and 51.33% were female. Median CRP (IQR) was 1.94 mg/L (0.83, 4.45) and median CRP of Q1-Q4 was 0.31 (0.21, 0.41), 0.85 (0.67, 1.08), 2.2 (1.72, 2.84), and 6.5 (4.73, 10.29), respectively (P _trend <0.0001). Up to 37% of the study population had HTN. Hypertensive patients had significantly higher SBP and DBP compared to their non-hypertensive counterparts (SBP 133±21 vs. 119±16; mean±SEM_diff 15±0.42 mmHg and DBP 77±13 vs. 73±10, mean_diff 5±0.26). Median eGFR was 98 mL/min/1.73 m² (76, 123). After adjusting for age (< vs. ≥65), gender, race (non-Black vs. Black), BMI, HbA1c, mean SBP and DBP, total cholesterol, serum albumin, serum ferritin, level of education, the ratio of family income to poverty, and an interaction term between age and race, participants with CRP in Q2, 3, and 4 had higher odds of worsening one more consecutive CKD stage from all cumulative below CKD stages compared to participants with CRP in Q1 (adjusted OR_Q2 1.450119 (1.20, 1.76), P <0.0001; OR_Q3 1.46 (1.21, 1.78, P <0.0001; OR_Q4 1.32 (1.07, 1.62), P 0.009). With subgroup analyses, only non-obese participants with HTN had worsening CKD stages with higher quartile of CRP (aOR_Q2 1.53 (1.02, 2.28), P 0.038; aOR_Q3 1.68 (1.129, 2.50), P 0.011; aOR_Q4 1.77, (1.14, 2.75), P 0.011). Race was identified as an effect modifier with decreased odds of worsening CKD stages observed in Black participants ≥65 years old in non-obese participants with HTN (P_interaction 0.038).

Conclusions: CRP is positively associated with CKD stages in non-obese participants with HTN, especially Black elderly participants.