Identification of volume overload hospitalizations among hemodialysis patients using administrative claims: a validation study

Table 2 Study cohort characteristics

Characteristics	All N = 315^a	Volume overloaded at admission^b n = 77 (24.4 %)	Not volume overloaded at admission^b n = 238 (75.6 %)
Age (years)	57 ± 14	57 ± 16	57 ± 14
Female	143 (45.4)	37 (48.1)	106 (44.5)
Race
Black	195 (61.9)	45 (58.4)	150 (63.0)
White	82 (26.0)	22 (28.6)	60 (25.2)
Other	38 (12.1)	10 (13.0)	28 (11.8)
Medicare as primary payer	266 (84.4)	62 (80.5)	204 (85.7)
History of diabetes^c	119 (37.8)	30 (39.0)	89 (37.4)
History of hypertension^c	217 (68.9)	64 (83.1)	153 (64.3)
History of arterial disease^c	150 (47.6)	43 (55.8)	107 (45.0)
History of heart failure^c	143 (45.4)	60 (77.9)	83 (34.9)
Length of hospital stay (days)^d	4 (2–8)	3 (2–6)	4 (2–8)
Admitting service
Medicine	257 (81.6)	74 (96.1)	183 (76.9)
Surgery	58 (18.4)	3 (3.9)	55 (23.1)
# of billed ICD-9 discharge diagnosis codes	14 (11–19)	16 (12–21)	13 (10–18)
Dialysis CPT procedure code billed on day of admission or the following day^e	150 (48.5) [N = 309]	42 (56.0) [n = 75]	108 (46.2) [n = 234]
Recent TTE ejection fraction^f
< 35 %	4 (6.1)	3 (21.4)	1 (1.9)
35–54 %	30 (45.5)	4 (28.6)	27 (50.0)
≥ 55 %	32 (48.5) [N = 66]	7 (50.0) [n = 14]	25 (48.1) [n = 52]

Values presented as mean ± standard deviation, median (quartile 1 – quartile 3) or n (%)
Abbreviations: CPT Current Procedural Terminology, ICD-9 International Classification of Diseases, Ninth Revision, TTE transthoracic echocardiogram
^aExcept where noted
^bVolume overload status at hospital admission based on clinical adjudication
^cComorbid conditions were captured using all available administrative data occurring before the sampled hospitalization. ICD-9 codes for: diabetes included 250.xx; hypertension included 401.xx-405.xx (except 402.11), 402.91, 404.11, 404.13, 404.91, 404.93; arterial disease included 410.xx, 414.0x, 429.2x, 429.5x, 429.7x, 440.x, 440.2x, 440.3x, 440.8x, 440.9x, 443.9x; and heart failure included 398.91, 402.x1, 404.x1, 404.x3, 428.xx
^dLength of hospital stay was computed as the discharge date minus the admission date. Patients admitted and discharged on the same day were assigned a length of stay = 0.5 days
^eSix patients were admitted and discharged on the same day and were excluded from this computation because we were unable to determine if they received dialysis on the day following admission using inpatient administrative claims data. Dialysis CPT procedure codes used to identify inpatient dialysis treatments include: 90935, 90937, 90945 and 90947
^fTTE conducted ≤1 year before sampled hospital admission

ISSN: 1471-2369