RT-PCR cycle threshold value in combination with visual scoring of chest computed tomography at hospital admission predicts outcome in COVID-19

Figures & data

Figure 1. Overview of the inclusion process. After exclusion, 286 patients remained that fulfilled the inclusion criteria and with data available. CT: computed tomography; Ct: cycle threshold.

Table 1. Patient characteristics.

Variable	Total (n = 286)	ICU/death (n = 87)	Not ICU/death (n = 199)
Female	125 (44%)	31 (36%)	94 (47%)
Age in years	61 (49-74)	68 (54-78)	60 (48-72)
Malignancy	26 (9%)	5 (6%)	21 (11%)
Diabetes mellitus	83 (29%)	32 (37%)	51 (26%)
Chronic kidney disease	8 (3%)	4 (5%)	4 (2%)
Plegia or previous stroke	13 (5%)	7 (8%)	6 (3%)
Ct value	27.5 (23.2–32.0)	25.7 (21.1–30.0)	28.8 (24.3–33.7)
CRP [mg/L] (n = 285)	71 (36–126)	107 (53–168)	61 (31–110)
WBC [x10^9/L] (n = 283)	5.8 (4.5–7.8)	6.4 (4.8–8.5)	5.6 (4.2–7.7)
Lymphocyte count [x10^9/L] (n = 284)	0.9 (0.7–1.2)	0.9 (0.7–1.1)	0.9 (0.7–1.3)
Ferritin [µg/L] (n = 244)	541 (253–1061)	842 (381–1397)	485 (220–775)
D-dimer [mg/L] (n = 265)	0.8 (0.5–1.2)	0.9 (0.6–1.6)	0.7 (0.0–1.2)
LDH [µkat/L] (n = 267)	5.0 (4.0–6.7)	6.5 (4.6–8.4)	4.7 (3.8–5.8)
CT score < 25%	187 (65%)	34 (39%)	153 (77%)
CT score 25-50%	68 (24%)	31 (36%)	37 (19%)
CT score > 50%	31 (11%)	22 (25%)	9 (5%)
Symptom duration [days]	7 (5–11)	7 (5–9)	8 (6–11)

Values are expressed as number (%) or median (interquartile range). Abbreviations: Ct: cycle threshold; ICU: intensive care unit; CRP: C-reactive protein; LDH: lactate dehydrogenase; WBC: white blood cell count; CT: computed tomography.

Table 2. Association between extracted variables and ICU admission or death.

Variable	Full multiple model coefficient	p value	Stepwise multiple model coefficient	p value
Female	0.61	.15
Age in years	0.017	.22	0.019	.049
Malignancy	−1.3	.17
Diabetes mellitus	0.49	.28
Chronic kidney disease	−0.075	.95
Plegia or previous stroke	−0.72	.49
Ct value	−0.13	<.001	−0.13	<.001
CRP [mg/L] (n = 285)	0.0032	.34	0.0062	.0037
WBC [x10^9/L] (n = 283)	0.011	.89
Lymphocyte count [x10^9/L] (n = 284)	−0.26	.60
Ferritin [µg/L] (n = 244)	−3.6 × 10^-05	.86
D-dimer [mg/L] (n = 265)	0.023	.67
LDH [µkat/L] (n = 267)	0.23	.061
CT score < 25% (reference)	N/A	N/A	N/A	N/A
CT score 25-50%	1.1	.032	1.4	<.001
CT score > 50%	2.9	<.001	2.4	<.001
Symptom duration [days]	−0.19	.0058

Significant p values are shown in bold. Ct: cycle threshold; ICU: intensive care unit; CRP: C-reactive protein; LDH: lactate dehydrogenase; WBC: white blood cell count; CT: computed tomography.

Figure 2. Relation between degree of lung involvement on chest CT images (x axis) and Ct value at admission (y axis). Boxes show median and interquartile range, whiskers represent range. Abbreviations: CT = computed tomography, Ct = cycle threshold.

Figure 3. Univariate regressions with proportion of patients reaching the outcome ICU admission or death within 60 days as dependent variable (y axis) and Ct value as independent variable (x axis), for all patients (a) and in groups based on degree of lung involvement (b–d). Regarding b-d, a significant association was demonstrated for <25% (b) and 25–50% (c) but not for >50% (d). Abbreviations: ICU = intensive care unit, Ct = cycle threshold.

Figure 4. ROC curves for the outcome ICU admission or death 60 days post hospital admission. Explanatory variables are Ct value, CRP, degree of lung involvement in chest CT images or combinations of the latter with either Ct value or CRP. The y axis represents sensitivity and the x axis 1-specificity. ICU: intensive care unit; Ct: cycle threshold; CRP: C-reactive protein; CT: computed tomography.