Table 1.

Baseline characteristics

CharacteristicOverall cohortPortal userNonuserP Valued
Patients, n (%)28031098 (39)1705 (61)
Age (yr)61±1758±1663±18<0.001
Women1387 (49)549 (50)838 (49)0.66
Race
 White2200 (78)952 (87)1248 (73)<0.001
 Black519 (19)114 (10)405 (24)
 Other84 (3)32 (3)52 (3)
Married1512 (54)688 (63)824 (48)<0.001
Insurance<0.001
 Private1309 (47)625 (57)684 (40)
 Medicaid201 (7)51 (5)150 (9)
 Medicare1108 (40)361 (33)747 (44)
 Self-pay/uninsured185 (7)61 (6)124 (7)
Median household income ($1000)46.8 (38.7–58.3)48.7 (39.7–63.2)45.6 (37.6–55.6)<0.001
Diabetes mellitus1101 (39)395 (36)706 (41)0.004
Hypertension2487 (89)977 (89)1510 (89)0.73
Hyperlipidemia1730 (62)706 (64)1024 (60)0.02
Coronary artery disease623 (22)217 (20)406 (24)0.01
Congestive heart failure342 (12)99 (9)243 (14)<0.001
Cerebrovascular disease 715 (26)299 (27)416 (24)0.09
Peripheral vascular disease358 (13)134 (12)224 (13)0.46
Tobacco use450 (16)131 (12)319 (19)<0.001
CKD stagea0.006
 Preserved eGFR/no proteinuria331 (12)151 (14)180 (11)
 1 and 2320 (12)137 (13)183 (11)
 3a665 (24)280 (26)385 (23)
 3b750 (27)291 (27)459 (28)
 4499 (18)168 (15)331 (20)
 5 (non–dialysis-dependent)155 (6)54 (5)101 (6)
Kidney transplant376 (13)211 (19)165 (10)<0.001
Nephrolithiasis300 (11)137 (12)163 (10)0.02
Charlson comorbidity index5.7±2.35.6±2.35.7±2.30.25
Systolic BP (mmHg)129 (118–142)128 (118–140)130 (120–142)0.002
Diastolic BP (mmHg)76 (68–82)77 (70–84)75 (68–82)0.02
Serum creatinineb (mg/dl)1.5 (1.1–2.0)1.4 (1.0–1.9)1.5 (1.1–2.1)<0.001
eGFRb (ml/min per 1.73 m2)44 (30–62)47 (32–66)42 (29–60)<0.001
Dipstick proteinuria (≥1+)c 1032 (37)362 (33)670 (39)<0.001
Median follow-up duration (yr)2.3 (1.2–3.3)2.7 (1.5–3.3)2.1 (1.1–3.2)<0.001
Nephrology office visits/yr2.9 (1.8–5.2)2.7 (1.8–4.3)3.1 (1.9–5.8)<0.001
University-affiliated PCP1375 (49)623 (57)752 (44)<0.001
Outpatient visits with a university-affiliated provider (excluding nephrology)9 (3–19)11 (4–23)8 (2–17)<0.001
Baseline ACEi/ARB use1161 (41)462 (42)699 (41)0.57
  • Continuous variables are presented as means±SDs or medians and interquartile ranges. Categorical variables are expressed as frequencies and percentages. ACEi/ARB, angiotensin-converting enzyme inhibitor/angiotensin receptor blocker.

  • a n=2720. When CKD staging could not be performed because of missing eGFR/dipstick, International Classification of Diseases, Ninth Revision, billing codes were used to categorize CKD stage if available.

  • b n=2668.

  • c n=2742.

  • d Chi-square or Wilcoxon-Mann-Whitney test used as appropriate.