Hi All, I am conducting a time series analysis on rates of health care utilization, I understand PROC AUTOREG is the most appropriate option in SAS. However, I do not have SAS/ETS. I have read several articles that use PROC Reg and call DWPROB to test for autocorrelation. Other sources have used Proc GLM or Proc GLIMMIX, but I do not think these can account for autocorrelation. We have designed this study well, but the intervention itself may not be strong. Are there any SAS alternative(s) for PROC Autoreg (not in SAS/ETS) that I can leverage. The proc reg and proc glimmix models are: PROC REG DATA = DATA;
MODEL CHANGE = TIME POST TIME_AFTER / DWPROB;
RUN; PROC GLIMMIX DATA = DATA; MODEL CHANGE = TIME POST TIME_AFTER/ SOLUTION CHISQ CORRB; RANDOM _RESIDUAL_; RUN; The Darwin & Watson test returns a value of 1.980, which suggests to me there is no autocorrelation between these variables and the outcome. PROC Reg and Prog GLIMMIX produce the same result - I am not sure if this is correct. Parameter Estimates Effect, Estimate, Standard Error, DF, t Value, Pr > |t| Intercept, 0.03472, 0.1190, 80, 0.29, 0.7713 Time, 0.01221, 0.004228, 80, 2.89, 0.0050 Post, 0.04177, 0.1800, 80, 0.23, 0.8171 time_after, -0.022390, .007764, 80, -2.88, 0.0050 This output would then suggest that the intervention resulted in a statically significant reduction of rates, albeit very small (-2% reduction). Looking forward to your ideas, questions, concerns, clarifications, all! Description of data: Change = change in rates of utilization between intervention and control Time = sequential number for the time period (84 records representing all months between 2011 and 2017) Post = 0 or 1 value for "no intervention" (0) or "intervention" (1) period Time_After = sequential number starting on the first intervention month on 01/01/2015 Full data below: SRC TIME EFFECTIVE_PERIOD POST PERIOD INT_RATE CONTROL_RATE INT_CLAIMS CONTROL_CLAIMS CHANGE CLAIMS_CHANGE TIME_AFTER ALL 1 1/1/2011 0 NO INTERVENTION 4.6 4.06 1377 1219 0.54 158 0 ALL 2 2/1/2011 0 NO INTERVENTION 3.91 3.67 1265 1111 0.24 154 0 ALL 3 3/1/2011 0 NO INTERVENTION 4.6 4.43 1566 1440 0.17 126 0 ALL 4 4/1/2011 0 NO INTERVENTION 3.42 3.86 1137 1155 -0.44 -18 0 ALL 5 5/1/2011 0 NO INTERVENTION 3.88 4.04 1339 1274 -0.16 65 0 ALL 6 6/1/2011 0 NO INTERVENTION 3.69 4.28 1182 1207 -0.59 -25 0 ALL 7 7/1/2011 0 NO INTERVENTION 3.79 3.56 1208 1027 0.23 181 0 ALL 8 8/1/2011 0 NO INTERVENTION 3.62 3.62 1229 1102 0 127 0 ALL 9 9/1/2011 0 NO INTERVENTION 4.57 4.15 1386 1129 0.42 257 0 ALL 10 10/1/2011 0 NO INTERVENTION 4.47 4.23 1354 1220 0.24 134 0 ALL 11 11/1/2011 0 NO INTERVENTION 4.86 4.24 1459 1256 0.62 203 0 ALL 12 12/1/2011 0 NO INTERVENTION 3.94 3.85 1233 1129 0.08 104 0 ALL 13 1/1/2012 0 NO INTERVENTION 4.59 3.84 1473 1227 0.75 246 0 ALL 14 2/1/2012 0 NO INTERVENTION 4.41 4.1 1369 1333 0.31 36 0 ALL 15 3/1/2012 0 NO INTERVENTION 4.51 4.57 1487 1405 -0.07 82 0 ALL 16 4/1/2012 0 NO INTERVENTION 4.18 4.02 1346 1310 0.16 36 0 ALL 17 5/1/2012 0 NO INTERVENTION 4.97 4.65 1664 1411 0.33 253 0 ALL 18 6/1/2012 0 NO INTERVENTION 4.62 3.81 1409 1228 0.81 181 0 ALL 19 7/1/2012 0 NO INTERVENTION 3.9 4.17 1254 1269 -0.27 -15 0 ALL 20 8/1/2012 0 NO INTERVENTION 4.21 3.74 1267 1151 0.47 116 0 ALL 21 9/1/2012 0 NO INTERVENTION 3.82 4.14 1104 1221 -0.32 -117 0 ALL 22 10/1/2012 0 NO INTERVENTION 4.39 4.27 1223 1276 0.13 -53 0 ALL 23 11/1/2012 0 NO INTERVENTION 3.95 4.05 1128 1156 -0.11 -28 0 ALL 24 12/1/2012 0 NO INTERVENTION 3.63 3.34 996 978 0.29 18 0 ALL 25 1/1/2013 0 NO INTERVENTION 5.12 3.88 1457 1025 1.24 432 0 ALL 26 2/1/2013 0 NO INTERVENTION 3.56 3.18 1106 894 0.38 212 0 ALL 27 3/1/2013 0 NO INTERVENTION 4.02 3.73 1206 1018 0.29 188 0 ALL 28 4/1/2013 0 NO INTERVENTION 4.37 4.09 1337 1130 0.28 207 0 ALL 29 5/1/2013 0 NO INTERVENTION 4.12 3.91 1204 1121 0.21 83 0 ALL 30 6/1/2013 0 NO INTERVENTION 3.86 3.58 1037 983 0.27 54 0 ALL 31 7/1/2013 0 NO INTERVENTION 3.83 3.89 1076 1022 -0.06 54 0 ALL 32 8/1/2013 0 NO INTERVENTION 3.96 4.07 1000 1118 -0.11 -118 0 ALL 33 9/1/2013 0 NO INTERVENTION 4.7 3.93 1084 991 0.77 93 0 ALL 34 10/1/2013 0 NO INTERVENTION 4.7 4.13 1213 1147 0.57 66 0 ALL 35 11/1/2013 0 NO INTERVENTION 4.24 3.19 1098 872 1.05 226 0 ALL 36 12/1/2013 0 NO INTERVENTION 3.71 3.16 935 831 0.54 104 0 ALL 37 1/1/2014 0 NO INTERVENTION 4.77 3.55 1263 891 1.22 372 0 ALL 38 2/1/2014 0 NO INTERVENTION 3.92 3.33 999 903 0.59 96 0 ALL 39 3/1/2014 0 NO INTERVENTION 5.26 4.54 1406 1135 0.72 271 0 ALL 40 4/1/2014 0 NO INTERVENTION 5.01 4.64 1339 1219 0.37 120 0 ALL 41 5/1/2014 0 NO INTERVENTION 5.18 4.69 1317 1203 0.49 114 0 ALL 42 6/1/2014 0 NO INTERVENTION 4.48 4.39 1175 1061 0.09 114 0 ALL 43 7/1/2014 0 NO INTERVENTION 4.39 4.36 1163 1092 0.03 71 0 ALL 44 8/1/2014 0 NO INTERVENTION 3.72 3.81 1033 1003 -0.09 30 0 ALL 45 9/1/2014 0 NO INTERVENTION 5.39 4.18 1415 1079 1.21 336 0 ALL 46 10/1/2014 0 NO INTERVENTION 5.18 4.41 1381 1210 0.77 171 0 ALL 47 11/1/2014 0 NO INTERVENTION 4.09 3.56 1155 923 0.53 232 0 ALL 48 12/1/2014 0 NO INTERVENTION 4.72 3.87 1278 1079 0.85 199 0 ALL 49 1/1/2015 1 INTERVENTION 5.15 4.22 1418 1106 0.93 312 1 ALL 50 2/1/2015 1 INTERVENTION 4.3 3.73 1174 994 0.57 180 2 ALL 51 3/1/2015 1 INTERVENTION 6.13 4.56 1631 1221 1.57 410 3 ALL 52 4/1/2015 1 INTERVENTION 5.42 4.66 1473 1300 0.77 173 4 ALL 53 5/1/2015 1 INTERVENTION 4.74 3.83 1276 1150 0.91 126 5 ALL 54 6/1/2015 1 INTERVENTION 4.81 4.15 1325 1144 0.66 181 6 ALL 55 7/1/2015 1 INTERVENTION 4.81 4.25 1391 1131 0.56 260 7 ALL 56 8/1/2015 1 INTERVENTION 4.49 4.44 1278 1221 0.05 57 8 ALL 57 9/1/2015 1 INTERVENTION 4.53 4.46 1252 1135 0.07 117 9 ALL 58 10/1/2015 1 INTERVENTION 5.52 4.61 1493 1245 0.91 248 10 ALL 59 11/1/2015 1 INTERVENTION 4.59 4.33 1268 1200 0.26 68 11 ALL 60 12/1/2015 1 INTERVENTION 4.68 4.63 1363 1220 0.05 143 12 ALL 61 1/1/2016 1 INTERVENTION 4.81 4.2 1267 1168 0.61 99 13 ALL 62 2/1/2016 1 INTERVENTION 4.36 4.76 1241 1258 -0.41 -17 14 ALL 63 3/1/2016 1 INTERVENTION 6.01 4.84 1679 1370 1.17 309 15 ALL 64 4/1/2016 1 INTERVENTION 4.94 4.73 1408 1379 0.2 29 16 ALL 65 5/1/2016 1 INTERVENTION 4.84 4.49 1407 1263 0.35 144 17 ALL 66 6/1/2016 1 INTERVENTION 5.9 5.07 1472 1415 0.84 57 18 ALL 67 7/1/2016 1 INTERVENTION 5.06 4.73 1316 1344 0.33 -28 19 ALL 68 8/1/2016 1 INTERVENTION 5.59 4.98 1454 1338 0.61 116 20 ALL 69 9/1/2016 1 INTERVENTION 4.99 5.14 1321 1271 -0.16 50 21 ALL 70 10/1/2016 1 INTERVENTION 5.09 4.56 1343 1310 0.53 33 22 ALL 71 11/1/2016 1 INTERVENTION 4.95 4.41 1336 1174 0.54 162 23 ALL 72 12/1/2016 1 INTERVENTION 4.61 4.43 1289 1234 0.18 55 24 ALL 73 1/1/2017 1 INTERVENTION 4.4 4.58 1185 1356 -0.18 -171 25 ALL 74 2/1/2017 1 INTERVENTION 4.66 4.44 1247 1187 0.22 60 26 ALL 75 3/1/2017 1 INTERVENTION 5.59 4.89 1480 1399 0.7 81 27 ALL 76 4/1/2017 1 INTERVENTION 4.24 4.33 1170 1244 -0.09 -74 28 ALL 77 5/1/2017 1 INTERVENTION 5.7 4.64 1496 1336 1.06 160 29 ALL 78 6/1/2017 1 INTERVENTION 5.16 4.46 1451 1270 0.7 181 30 ALL 79 7/1/2017 1 INTERVENTION 4.41 3.92 1318 1200 0.49 118 31 ALL 80 8/1/2017 1 INTERVENTION 5.3 4.2 1455 1268 1.11 187 32 ALL 81 9/1/2017 1 INTERVENTION 5.17 4.65 1434 1276 0.52 158 33 ALL 82 10/1/2017 1 INTERVENTION 5.05 5.15 1379 1421 -0.1 -42 34 ALL 83 11/1/2017 1 INTERVENTION 5.27 4.89 1316 1367 0.38 -51 35 ALL 84 12/1/2017 1 INTERVENTION 4.35 4.2 1243 1196 0.15 47 36 Thank you! Some References: 1. (USES PROC GLIMMIX) Wong, EC. Analysing Phased Intervention with Segmented Regression and Stepped Wedge Deisngs: https://www.lexjansen.com/wuss/2014/74_Final_Paper_PDF.pdf 2. (USES PROC AUTOREG) Penfold, R. Use of Interrupted Time Series Analysis in Evaluating Health Care Quality Improvements https://www.academicpedsjnl.net/article/S1876-2859(13)00210-6/pdf
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