Performance of the Medical Priority Dispatch System® in Identifying Patients Requiring Chest Compressions at Overdose Prevention Services: A Retrospective Cohort Study

Figures & data

Figure 1. Participant flow.

BCEHS = British Columbia Emergency Health Services; OPS = Overdose Prevention Services; OHCA = Out-of-Hospital Cardiac.

Table 1. Location-based patient characteristics.

Characteristic	Non-OPS (N = 1,643,735) n (%)	OPS (N = 4,911) n (%)	p-value
Age			<0.01^a
0–20	102,994 (6.3)	72 (1.5)
21 – 40	312,204 (19.0)	2,215 (45.1)
41 – 60	342,257 (20.9)	1,975 (40.3)
61 – 80	491,170 (29.8)	337 (6.7)
> 81	379,659 (23.1)	9 (0.2)
Unknown	15,451 (0.9)	312 (6.4)_
Sex			<0.01^a
Female	800,074 (48.7)	1,029 (21.0)
Male	840,675 (51.1)	3,858 (78.6)
Non-Binary	917 (0.1)	3 (<0.1)
Unknown	2,069 (0.1)	21 (0.1)
Time			<0.01^a
00:01 – 06:00	242,730 (17.2)	501 (10.2)
06:01 – 12:00	433,690 (24.0)	866 (17.6)
12:01 – 18:00	535,476 (32.5)	2,063 (42.0)
18:01–00:00	431,839 (26.3)	1,481 (30.2)
T-CPR Instructions			<0.01^a
Yes	48,431 (2.9)	626 (12.7)
No	1,595,304 (97.1)	4,285 (87.3)
OHCA			<0.01^b
Yes	27,727 (1.7)	3 (0.1)
No	1,616,008 (98.3)	4,908 (99.9)
Reason for OHCA^c			<0.01^b
Allergy	1 (<0.1)	0 (0)
Asphyxia	666 (<0.1)	0 (0)
Drowning	183 (<0.1)	0 (0)
Drug Poisoning	2,801 (10.1)	2 (66.6)
Electrocution	19 (<0.1)	0 (0)
Other Medical	1,516 (5.4)	0 (0)
Presumed Cardiac	13,141 (47.4)	1 (33.3)
Trauma	916 (3.3)	0 (0)
Not Specified	8,484 (30.6)	0 (0)
	Mean (SD)	Mean (SD)
Glasgow Coma Scale	14.4 (2.2)	12.9 (3.6)	<0.01^d
Respiratory Rate	19.2 (7.1)	17.0 (15.9)	0.64^d
SpO2	95.2 (8.2)	97.0 (4.5)	<0.01^d
Heart Rate	89.7 (23.2)	93.9 (19.6)	<0.01^d

Abbreviations: T-CPR = telephone cardiopulmonary resuscitation; OHCA = out-of-hospital cardiac arrest.

^a Chi-Squared.

^b Fishers exact test.

^c Recorded by BCEHS staff based on clinical impression at time of OHCA.

^d Independent t test.

Table 2. 2 × 2 tables by characteristic.

Overall
	OHCA	No OHCA
T-CPR Instructions	17,291	31,766
No T-CPR Instructions	10,439	1,589,150
Non-OPS Location
	OHCA	No OHCA
T-CPR Instructions	17,289	31,142
No T-CPR Instructions	10,438	1,584,866
OPS Location
	OHCA	No OHCA
T-CPR Instructions	2	624
No T-CPR Instructions	1	4,284
Non-Drug Poisoning Etiology
	OHCA	No OHCA
T-CPR Instructions	15,482	16,414
No T-CPR Instructions	10,083	1,536,058
Drug Poisoning Etiology
	OHCA	No OHCA
T-CPR Instructions	1,809	15,352
No T-CPR Instructions	356	53,092

Abbreviations: OHCA = Out of Hospital Cardiac Arrest; T-CPR = Telecommunicator Cardiopulmonary Resuscitation; OPS = Overdose Prevention Service.

Table 3. Test performance of MPDS® by characteristic.

		Location-Based Groups		Impression Code Groups
Measure	Overall	Non-OPS	OPS	Non-Drug Poisoning	Drug Poisoning
Sensitivity (%)	62.35 (61.78–62.93)	62.35 (61.78–62.93)	66.67 (9.43–99.16)	60.56 (59.96–61.16)	83.56 (81.93–85.09)
Specificity (%)	98.04 (98.02–98.06)	98.07 (98.05–98.09)	87.29 (86.32–88.21)	98.94 (98.93–98.96)	77.57 (77.26–77.88)
PPV	35.25 (34.92–35.57)	35.70 (35.37–36.03)	0.32 (0.14–0.72)	48.54 (48.09–48.99)	10.54 (10.32–10.76)
NPV	99.35 (99.33–99.36)	99.35 (99.34–99.36)	99.98 (99.88–100)	99.35 (99.34–99.36)	99.33 (99.27–99.39)
LR+	31.82 (31.37–32.27)	32.36 (31.89–32.27)	5.24 (2.34–11.71)	57.88 (56.84–58.94)	3.73 (3.64–3.81)
LR-	0.383 (0.378–0.389)	0.383 (0.379–0.389)	0.38 (0.08–1.89)	0.398 (0.392–0.404)	0.21 (0.19–0.23)
FPR	1.96 (1.94–1.98)	1.93 (1.91–1.95)	12.71 (11.79–13.68)	1.06 (1.04–1.07)	22.43 (22.12–22.74)

Abbreviations: OPS = overdose prevention service; PPV = positive predictive value; NPV = negative predictive value; LR+ = positive likelihood ratio; LR- = negative likelihood ratio; FPR = false positive rate.

%, (95% Confidence Interval).

Table

Public (n = 1,643,731)
	OHCA	No OHCA
T-CPR Instructions	17,286	31,142
No T-CPR Instructions	10,437	1,584,866
Supervised Consumption Site (n = 1,556)
	OHCA	No OHCA
T-CPR Instructions	0	212
No T-CPR Instructions	1	1,343
Overdose Prevention Site (n = 3,359)
	OHCA	No OHCA
T-CPR Instructions	2	416
No T-CPR Instructions	0	2,941

OHCA = Out of Hospital Cardiac Arrest; T-CPR = Telecommunicator Cardiopulmonary Resuscitation; OPS = Overdose Prevention Service.