Utility of Emergency Medical Dispatch (EMD) Telephone Screening in Identifying COVID-19 Positive Patients

Figures & data

Table 1. Study Population Patient Characteristics by COVID-19 Diagnosis

	Total Sample (n = 3,443)		COVID+ (n = 652)		COVID- (n = 2,791)
Demographic Variables	N	%*	N	%	N	%	P-value^β
Age, in years (mean, std.)	66.0	18.8	68.7	15.6	65.4	19.4	<0.0001
Gender							0.001
Female	1805	52.4	308	47.2	1497	53.6
Male	1630	47.3	340	52.2	1290	46.2
Unknown	8	0.2	5	0.6	4	0.1
Race							<0.0001
White	1016	29.5	146	22.4	870	31.2
Black	458	13.3	86	13.2	372	13.3
Other	595	17.3	136	20.9	459	16.4
Unknown/Not Documented	1374	39.8	284	43.6	1090	39.1
Hispanic							0.3
Yes	316	9.2	67	10.3	249	8.9
No	3127	90.8	585	89.7	2542	91.1
Insurance							0.2
Medicaid/State based	552	16.0	97	14.9	455	16.3
Medicare	578	16.8	127	19.5	451	16.2
Private	1066	30.9	203	31.1	863	30.9
Other	673	19.6	115	17.6	558	20.0
None Identified/Unknown/Missing	574	16.7	110	16.9	464	16.6
Medical History							0.09
Diabetes	622	18.1	134	20.6	488	17.5
Chronic lung disease	519	15.1	89	13.7	430	15.4
Cardiovascular disease	487	14.1	83	12.7	404	14.5
Neurological disorder, neurodevelopmental, intellectual disability	290	8.4	48	7.4	242	8.7
Other chronic disease	1039	30.2	209	32.1	830	29.7
None of the above conditions	276	8.0	59	9.1	217	7.8
Unknown/missing/not documented	210	6.1	30	4.6	180	6.5
More than one conditions							0.4
Yes	2266	65.8	421	64.6	1845	66.1
No	711	20.7	147	22.6	564	20.2
Not documented	466	13.5	84	12.9	382	13.7

* Percentages may not add up to 100% due to rounding.

^βP-value corresponds to Student’s t-test, Chi-square or Fisher’s exact tests where appropriate.

Table 2. EMS Encounter Characteristics by COVID-19 Diagnosis

	Total Sample (n = 3,443)		COVID+ (n = 652)		COVID- (n = 2,791)
EMS Encounter Variables	N	%*	N	%	N	%	P-value^β
Month							<0.0001
March 2020	705	20.5	215	33.0	490	17.6
April 2020	1245	36.2	363	55.7	882	31.6
May 2020	762	22.1	58	8.9	704	25.2
June 2020	731	21.2	16	2.5	715	25.6
Time of Day							0.3
00:00-07:59	335	9.7	54	8.3	281	10.1
08:00-15:59	2048	59.5	399	61.2	1649	59.1
16:00-23:59	1060	30.8	199	30.5	861	30.9
COVID-19 EMD Telephone Screening							<0.0001
Positive	2010	58.4	489	75.0	1521	54.5
Negative	1433	41.6	163	25.0	1270	45.5
PPE Donned							<0.0001
Full	975	28.3	385	59.1	590	21.1
Partial	2233	64.9	223	34.2	2010	72.0
Not documented	234	6.8	44	6.8	190	6.8
None	1	0.1	0	0.0	1	0.1
Dispatch code							<0.0001
Abdominal Pain	130	3.8	6	0.9	124	4.4
Breathing Problems	686	19.9	238	36.5	448	16.1
Cardiac/Respiratory Arrest	5	0.2	0	0.0	5	0.2
Chest Pain	193	5.6	13	2.0	180	6.5
Headache	21	0.6	3	0.5	18	0.6
Heart Problems	99	2.9	12	1.8	87	3.1
Sick Person	494	14.4	125	19.2	369	13.2
Pandemic Flu	1028	29.9	191	29.3	837	30.0
Unknown Problem	1	0.1	0	0.0	1	0.1
Unconscious/Fainting	155	4.5	19	2.9	136	4.9
Other	631	18.3	45	6.9	586	21.0
Priority level							<0.0001
High	2426	70.5	534	81.9	1892	67.8
Low	1017	29.5	118	18.1	899	32.2
Service level							<0.0001
ALS	2446	71.0	534	81.9	1912	68.5
BLS	997	29.0	118	18.1	879	31.5
Disposition							0.6
Assist	1	0.1	0	0.0	1	0.0
Treated and Transferred Care	3	0.1	0	0.0	3	0.1
Treated/Transported	3439	99.9	652	100.00	2787	99.9
Transport Facility Type							0.04
Tertiary	2789	81.0	510	78.2	2279	81.7
Community	654	19.0	142	21.8	512	18.3

* Percentages may not add up to 100% due to rounding.

^βP-value corresponds to Chi-square or Fisher’s exact tests where appropriate.

Table 3. EMS Provider Assessments and Patient Vitals by COVID-19 Diagnosis

	Total Sample (n = 3,443)		COVID+ (n = 652)		COVID- (n = 2,791)
Assessments^α	N	%	N	%	N	%	P-value^β
Breathing rate normal	3034	88.1	520	79.8	2514	90.1	<0.0001
Breathing unlabored	3057	88.8	520	79.8	2537	90.9	<0.0001
Airway patent	3366	97.8	628	96.3	2738	98.1	0.02
Skin temperature normal	3115	90.5	554	85.0	2561	91.8	<0.0001
Lungs clear	3016	87.6	505	77.5	2511	90.0	<0.0001
Patient Vitals*	Median	Range	Median	IQR	Median	IQR
Respiratory rate(breaths/min)	18	4–60	20	18–24	18	16–20	<0.0001
Pulse (beats/min)	90	0–195	94	81–106	89	77–103	0.004
Oxygen Saturation (Sp02)	97	2–100	95	90–97	97	95–99	<0.0001

^αResponse categories: Yes vs. No vs. Not documented.

^βP-value corresponds to Student’s t-test, Wilcoxon rank sum, Chi-square or Fisher’s exact tests where appropriate.

* Sample sizes: Respirations (n = 3418), Pulse (n = 3431), Sp02 (n = 3394).

Table 4. Estimates of Sensitivity, Specificity, Positive and Negative Predictive Value of the Emergency Medical Dispatch COVID-19 Telephone Screening (n = 3,443)

	COVID Positive
Screen Positive	Yes		No		Total
	N	%	N	%
Yes	489	14.2	1,521	44.2	2,010
No	163	4.7	1,270	36.9	1,433
Total	652		2,791
Statistic		Estimate		95% CI
Sensitivity		75.0%		71.7%, 78.3%
Specificity		45.5%		43.7%, 47.4%
Positive Predictive Value		24.3%		22.5%, 26.0%
Negative Predictive Value		88.6%		87.0%, 90.3%