Table 2

Accuracy of case ascertainment algorithms in identifying individuals experiencing homelessness

Reference standard definition: housing episode (n = 144 148 overall, with 3443 homeless episodes)
Algorithm definitionTPFPFNTNSensitivity (%)
(95% CI)
Specificity (%)
(95% CI)
PPV (%)(95% CI)NPV (%)(95% CI)LR+
1 indicator+/−0 days3725283071140 17710.8 (9.8 to 11.9)99.6 (99.6 to 99.7)41.3 (38.2 to 44.6)97.9 (97.8 to 97.9)28.8
1 indicator+/−15 days4825912961140 11414.0 (12.9 to 15.2)99.6 (99.5 to 99.6)44.9 (42.0 to 47.9)97.9 (97.9 to 98.0)33.3
1 indicator+/−45 days6196652824140 04018.0 (16.7 to 19.3)99.5 (99.5 to 99.6)48.2 (45.5 to 50.9)98.0 (98.0 to 98.1)38.0
1 indicator+/−90 days7187652725139 94020.9 (19.5 to 22.2)99.5 (99.4 to 99.5)48.4 (45.9 to 51.0)98.1 (98.0 to 98.2)38.4
1 indicator+/−180 days8618972582139 80825.0 (23.6 to 26.5)99.4 (99.3 to 99.4)49.0 (46.6 to 51.3)98.2 (98.1 to 98.3)39.2
1 indicator OR postal code+/−0 days4506792993140 02613.1 (12.0 to 14.2)99.5 (99.5 to 99.6)39.9 (37.0 to 42.7)97.9 (97.8 to 98.0)27.1
1 indicator OR postal code+/−15 days5727582871139 94716.6 (15.4 to 17.9)99.5 (99.4 to 99.5)43.0 (40.4 to 45.7)98.0 (97.9 to 98.1)30.8
1 indicator OR postal code+/−45 days7148452729139 86020.7 (19.4 to 22.1)99.4 (99.4 to 99.4)45.8 (43.3 to 48.3)98.1 (98.0 to 98.2)34.5
1 indicator OR postal code+/−90 days8249672619139 73823.9 (22.5 to 25.4)99.3 (99.3 to 99.4)46.0 (43.7 to 48.3)98.2 (98.1 to 98.2)34.8
1 indicator OR postal code+/−180 days99411352449139 57028.9 (27.4 to 30.4)99.2 (99.1 to 99.2)46.7 (44.6 to 48.8)98.3 (98.2 to 98.3)35.8
1 CIHI indicator+/−0 days3684663075140 23910.7 (9.7 to 11.8)99.7 (99.6 to 99.7)44.1 (40.8 to 47.5)97.9 (97.8 to 97.9)36.9
1 CIHI indicator+/−15 days4775282966140 17713.9 (12.7 to 15.0)99.6 (99.6 to 99.7)47.5 (44.4 to 50.6)97.9 (97.9 to 98.0)39.6
1 CIHI indicator+/−45days 613 595 2830 140 11 0 17.8 (16.6 to 19.1) 99.6 (99.5 to 99.6) 50.7 (47.9 to 53.6) 98.0 (97.9 to 98.1) 42.0
1 CIHI indicator+/−90 days7106932733140 01220.6 (19.3 to 22.0)99.5 (99.5 to 99.5)50.6 (48.0 to 53.2)98.1 (98.0 to 98.2)41.7
1 CIHI indicator+/−180 days8528222591139 88324.8 (23.3 to 26.2)99.4 (99.4 to 99.5)50.9 (48.5 to 53.3)98.2 (98.1 to 98.3)41.8
1 CIHI indicator OR postal code+/−0 days4445752999140 13012.9 (11.8 to 14.1)99.6 (99.6 to 99.6)43.6 (40.6 to 46.6)97.9 (97.8 to 98.0)32.3
1 CIHI indicator OR postal code+/−15 days5666522877140 05316.4 (15.2 to 17.7)99.5 (99.5 to 99.6)46.5 (43.7 to 49.3)98.0 (97.9 to 98.1)36.9
1 CIHI indicator OR postal code+/−45 days7077342736139 97120.5 (19.2 to 21.9)99.5 (99.4 to 99.5)49.1 (46.5 to 51.6)98.1 (98.0 to 98.2)42.1
1 CIHI indicator OR postal code+/−90 days8178522626139 85323.7 (22.3 to 25.2)99.4 (99.4 to 99.4)49.0 (46.6 to 51.3)98.2 (98.1 to 98.2)41.9
1 CIHI indicator OR postal code+/−180 days98510172458139 68828.6 (27.1 to 30.1)99.3 (99.2 to 99.3)49.2 (47.0 to 51.4)98.3 (98.2 to 98.3)42.4
Reference standard definition: annual housing experience (n = 4 91 213 calendar years overall, with 2290 homeless years)
Algorithm definitionTPFPFNTNSensitivity (%)
(95% CI)
Specificity (%)
(95% CI)
PPV (%)(95% CI)NPV (%)(95% CI)LR+
1 indicator+/−0 days4293341861488 58918.7 (17.2 to 20.4)99.9 (99.9 to 99.9)56.2 (52.7 to 59.7)99.6 (99.6 to 99.6)274.2
1 indicator+/−15 days4543521836488 57119.8 (18.2 to 21.5)99.9 (99.9 to 99.9)56.3 (52.9 to 59.7)99.6 (99.6 to 99.6)275.4
1 indicator+/−45 days4874061803488 51721.3 (19.6 to 23.0)99.9 (99.9 to 99.9)54.5 (51.3 to 57.8)99.6 (99.6 to 99.6)256.1
1 indicator+/−90 days5294721761488 45123.1 (21.4 to 24.9)99.9 (99.9 to 99.9)52.8 (49.8 to 55.9)99.6 (99.6 to 99.7)239.3
1 indicator+/−180 days5905881700488 33525.8 (24.0 to 27.6)99.9 (99.9 to 99.9)50.1 (47.2 to 52.9)99.7 (99.6 to 99.7)214.2
1 indicator OR postal code+/−0 days5124331778488 49022.4 (20.7 to 24.1)99.9 (99.9 to 99.9)54.2 (51.0 to 57.3)99.6 (99.6 to 99.7)252.5
1 indicator OR postal code+/−15 days5434581747488 46523.7 (22.0 to 25.5)99.9 (99.9 to 99.9)54.2 (51.1 to 57.3)99.6 (99.6 to 99.7)253.1
1 indicator OR postal code+/−45 days5815251709488 39825.4 (23.6 to 27.2)99.9 (99.9 to 99.9)52.5 (49.6 to 55.5)99.7 (99.6 to 99.7)236.3
1 indicator OR postal code+/−90 days6296101661488 31327.5 (25.7 to 29.3)99.9 (99.9 to 99.9)50.8 (48.0 to 53.5)99.7 (99.6 to 99.7)220.2
1 indicator OR postal code+/−180 days7077541583488 16930.9 (29.0 to 32.8)99.9 (99.8 to 99.9)48.4 (45.8 to 51.0)99.7 (99.7 to 99.7)200.2
1 indicator+/−0 day OR PSTLYEAR postal code5883561702488 56725.7 (23.9 to 27.5)99.9 (99.9 to 99.9)62.3 (59.2 to 65.3)99.7 (99.6 to 99.7)352.6
1 indicator+/−15 days OR PSTLYEAR postal code7064021584488 52130.8 (29.0 to 32.8)99.9 (99.9 to 99.9)63.7 (60.8 to 66.5)99.7 (99.7 to 99.7)375.0
1 indicator+/−45 days OR PSTLYEAR postal code7344521556488 47132.1 (30.2 to 34.0)99.9 (99.9 to 99.9)61.9 (59.1 to 64.6)99.7 (99.7 to 99.7)346.7
1 indicator+/−90 days OR PSTLYEAR postal code7665181524488 40533.4 (31.5 to 35.4)99.9 (99.9 to 99.9)59.7 (56.9 to 62.3)99.7 (99.7 to 99.7)315.7
1 indicator+/−180 days OR PSTLYEAR postal code8166331474488 29035.6 (33.7 to 37.6)99.9 (99.9 to 99.9)56.3 (53.7 to 58.8)99.7 (99.7 to 99.7)275.2
1 CIHI indicator+/−0 days4233001867488 62318.5 (16.9 to 20.1)99.9 (99.9 to 99.9)58.5 (54.9 to 62.0)99.6 (99.6 to 99.6)301.0
1 CIHI indicator+/−15days 448 315 1842 488608 19.6 (18.0 to 21.2) 99.9 (99.9 to 99.9) 58.7 (55.2 to 62.2) 99.6 (99.6 to 99.6) 303.6
1 CIHI indicator+/−45 days4803581810488 56521.0 (19.3 to 22.7)99.9 (99.9 to 99.9)57.3 (53.9 to 60.6)99.6 (99.699.6)286.3
1 CIHI indicator+/−90 days5214051769488 51822.8 (21.1 to 24.5)99.9 (99.9 to 99.9)56.3 (53.0 to 59.4)99.6 (99.6 to 99.7)274.7
1 CIHI indicator+/−180 days5815191709488 40425.4 (23.6 to 27.2)99.9 (99.9 to 99.9)52.8 (49.9 to 55.8)99.7 (99.6 to 99.7)239.0
1 CIHI indicator OR postal code+/−0 days5083701782488 55322.2 (20.5 to 23.9)99.9 (99.9 to 99.9)57.9 (54.6 to 61.1)99.6 (99.6 to 99.7)293.1
1 CIHI indicator OR postal code+/−15 days5393901751488 53323.5 (21.8 to 25.3)99.9 (99.9 to 99.9)58.0 (54.8 to 61.2)99.6 (99.6 to 99.7)295.1
1 CIHI indicator OR postal code+/−45 days5764421714488 48125.2 (23.4 to 27.0)99.9 (99.9 to 99.9)56.6 (53.5 to 59.6)99.7 (99.6 to 99.7)278.2
1 CIHI indicator OR postal code+/−90 days6225021668488 42127.2 (25.4 to 29.0)99.9 (99.9 to 99.9)55.3 (52.4 to 58.2)99.7 (99.6 to 99.7)264.5
1 CIHI indicator OR postal code+/−180 days6996341591488 28930.5 (28.7 to 32.4)99.9 (99.9 to 99.9)52.4 (49.8 to 55.1)99.7 (99.7 to 99.7)235.4
1 CIHI indicator+/-0 day OR PSTLYEAR postal code5833221707488 60125.5 (23.7 to 27.3)99.9 (99.9 to 99.9)64.4 (61.2 to 67.5)99.7 (99.6 to 99.7)386.6
1 CIHI indicator+/−15 days OR PSTLYEAR postal code7013651589488 55830.6 (28.8 to 32.5)99.9 (99.9 to 99.9)65.8 (62.9 to 68.5)99.7 (99.7 to 99.7)410.0
1 CIHI indicator+/−45 days OR PSTLYEAR postal code7284041562488 51931.8 (29.9 to 33.7)99.9 (99.9 to 99.9)64.3 (61.5 to 67.0)99.7 (99.7 to 99.7)384.7
1 CIHI indicator+/−90 days OR PSTLYEAR postal code7604511530488 47233.2 (31.3 to 35.1)99.9 (99.9 to 99.9)62.8 (60.0 to 65.4)99.7 (99.7 to 99.7)359.8
1 CIHI indicator+/−180 days OR PSTLYEAR postal code8095641481488 35935.3 (33.4 to 37.3)99.9 (99.9 to 99.9)58.9 (56.3 to 61.5)99.7 (99.7 to 99.7)306.2
  • Bold lines indicate optimal case algorithm definitions.

  • CIHI, Discharge Abstract Database, National Ambulatory Care Reporting System or Ontario Mental Health Reporting System; FN, false negative (flagged as housed but truly homeless); FP, false positive (flagged as homeless but not truly homeless); LR+, positive likelihood ratio; NPV, negative predictive value; PPV, positive predictive value; PSTLYEAR, ICES PSTLYEAR postal code, indicating the best estimate of an individual’s postal code for the year using ICES databases; TN, true negative (flagged as housed and truly housed); TP, true positive (flagged as homeless and truly homeless).