Table 1.

Characteristics of the study population according to the potassium levels^a.

	Normokalemia (n = 212)	Mild hypokalemia (n = 76)	Severe hypokalemia (n = 18)	p-Valuesb
				p1	p2	p3	p4
Demographics
Age (median), years	64.0 (46.8–77.0)	65.0 (58.3–75.0)	73.5 (53.5–80.0)	0.266	0.448	0.241	0.123
Comorbidities
Hypertension, %	46.2	57.9	50.0	0.085	0.544	0.756	0.100
ARA2/ACEI, %	28.6	36.8	22.2	0.181	0.239	0.565	0.337
Diabetes, %	21.4	22.4	22.2	0.900	0.989	0.937	0.859
Obesity, %	38.3	31.0	17.6	0.376	0.273	0.091	0.108
Cardiovascular disease, %	13.8	9.2	16.7	0.266	0.356	0.738	0.445
Charlson comorbidity index ≥3, %	49.0	59.2	77.8	0.129	0.143	0.019*	0.027*
Clinical presentation
Clinical duration, daysc	7.0 (4.0–11.0)	5.5 (3.0–8.0)	3.0 (1.0–7.5)	0.513	0.098	0.029*	0.088
Fever, %	72.1	76.3	55.6	0.409	0.077	0.138	0.968
Dry cough, %	64.9	57.9	29.4	0.450	0.033*	0.004*	0.045*
Dyspnea, %	57.2	48.7	38.9	0.253	0.454	0.133	0.093
Diarrhea, %	24.0	28.0	22.2	0.450	0.620	0.864	0.597
Confusion, %	11.2	14.7	22.2	0.511	0.434	0.170	0.239
Fatigue, %	39.9	43.2	35.3	0.565	0.549	0.709	0.765
Myalgia/arthralgia, %	29.7	21.6	11.8	0.244	0.358	0.115	0.075
Anosmia/dysgeusia, %	13.6	11.0	5.9	0.627	0.530	0.362	0.387
Initial assessment
Oximetry on room air (%)	95.0 (92.0–97.0)	94.0 (91.0–97.0)	94.5 (90.5–96.8)	0.195	0.604	0.889	0.227
PaO2:FiO2	333.3 (276.1–400.0)	324.4 (277.3–371.4)	323.0 (276.0–407.0)	0.665	0.684	0.494	0.456
Respiratory rate, breaths/min	18.0 (16.0–24.0)	18.0 (15.3–25.0)	17.0 (16.0–27.0)	0.775	0.848	0.890	0.862
Systolic BP, mmHg	130.0 (115.8–141.3)	126.0 (108.5–153.5)	132.0 (115.3–159.0)	0.903	0.408	0.272	0.493
Diastolic BP, mmHg	78.5 (68.0–89.0)	73.0 (64.0–84.0)	81.5 (72.8–91.5)	0.032*	0.059	0.317	0.170
Heart rate, beats/min	94.0 (80.0–106.0)	94.0 (83.0–103.0)	96.5 (79.8–106.5)	0.665	0.628	0.817	0.766
CURB65	1.0 (0.0–2.0)	1.0 (0.0–3.0)	2.0 (0.3–2.8)	0.069	0.924	0.258	0.045*
eGFR, ml/min/m2	83.0 (56.2–90.0)	78.7 (53.6–90.0)	76.1 (37.5–90.0)	0.972	0.335	0.293	0.586
eGFR <60 mL/min/m2, %	26.8	28.9	47.1	0.891	0.149	0.075	0.331
Lymphocytes, 109 cells/liter	1.09 (0.79–1.41)	0.88 (0.64–1.31)	1.08 (0.49–1.54)	0.025*	0.758	0.478	0.018*
C-reactive protein, mg/dl	5.7 (2.5–11.9)	7.7 (2.9–14.4)	7.8 (2.0–15.2)	0.256	0.931	0.623	0.231
Procalcitonin, ng/mL	0.10 (0.05–0.18)	0.13 (0.06–0.20)	0.22 (0.06–0.36)	0.240	0.327	0.129	0.075
Ferritin, mg/l	618.0 (293.0–1184.0)	961.0 (470.3–1442.5)	796.5 (353.5–2935.0)	0.008*	0.905	0.160	0.002*
Interleukin 6, pg/mL	21.50 (9.25–46.75)	47.0 (18.50–69.75)	28.0 (4.50–105.50)	0.001*	0.824	0.358	0.002*
Lactate dehydrogenase, U/l	269.0 (218.0–360.0)	274.0 (238.0–371.0)	265.0 (240.0–413.0)	0.218	0.971	0.686	0.198
D-dimer, mg/mL	0.59 (0.39–1.20)	0.75 (0.46–1.52)	0.85 (0.62–2.73)	0.198	0.287	0.051	0.046*
Troponin T, ng/l	9.0 (6.0–20.5)	11.5 (7.0–22.8)	27.0 (11.0–55.0)	0.384	0.025*	0.005*	0.033*
Brain natriuretic peptide, pg/mL	133.0 (30.8–693.0)	176.0 (48.0–905.0)	1502.0 (81.0–2964.0)	0.312	0.072	0.014*	0.040*
Creatine phosphokinase, U/l	78.0 (51.0–143.5)	87.5 (63.0–144.3)	108.5 (34.3–449.5)	0.422	0.715	0.597	0.317
Opacities >50% of lung surface on X-ray, %	24.7	19.4	18.8	0.438	0.953	0.592	0.327

ARA2/ACEI, angiotensin II receptor antagonists/angiotensin-converting enzyme inhibitors; BP, blood pressure; eGFR, estimated glomerular filtration rate. Data shown as % or median (interquartile range), unless specified otherwise. *p <  0.05, statistically significant difference.

^aSevere hypokalemia (K⁺ <3 mmol/l), mild hypokalemia (K⁺ 3–3.5 mmol/l), and normokalemia (K⁺ >3.5 mmol/l). Hypokalemia was defined as K⁺ ≤3.5 mmol/l (i.e., severe hypokalemia plus mild hypokalemia).

^bThe Mann–Whitney U-test and Chi-square test were used for group comparisons: p1, mild hypokalemia vs normokalemia; p2, mild hypokalemia vs severe hypokalemia; p3, severe hypokalemia vs normokalemia; p4, hypokalemia vs normokalemia.

^cDays of symptoms before admission.