Table 3.
Validity of the Diagnostic Codes for IBD, CD and UC in the NPR Using Number of Hospital Admissions/Out-Patient Clinic Visits with a Main Discharge Diagnosis Registered in the NPR as Criteria
| No. of Cases According to NPR | No. of Confirmed Cases in the Patient Record | No. of Cases Lost Compared to Using 1 Diagnosis as Criteria | PPV (95% CI) | |
|---|---|---|---|---|
| Including MC as IBD casea | ||||
| At least one diagnosis of IBD Female Male |
277 156 121 |
217 124 93 |
– – – |
0.78 (0.73–0.83) 0.80 (0.72–0.86) 0.77 (0.68–0.84) |
| At least 2 diagnoses of IBD | 157 | 141 | 76 | 0.90 (0.84–0.94) |
| At least 3 diagnoses of IBD Female Male |
102 45 57 |
99 43 56 |
118 81 37 |
0.97 (0.92–0.99) 0.96 (0.85–1.00) 0.98 (0.91–1.00) |
| Excluding MC as caseb | ||||
| At least one diagnosis of IBD Female Male |
277 156 121 |
161 76 85 |
– – – |
0.58 (0.52–0.64) 0.49 (0.41–0.57) 0.70 (0.61–0.78) |
| At least 2 diagnoses of IBD | 157 | 123 | 38 | 0.78 (0.71–0.85) |
| At least 3 diagnoses of IBD Female Male |
102 45 57 |
94 39 55 |
67 37 30 |
0.92 (0.85–0.97) 0.87 (0.73–0.95) 0.97 (0.88–1.00) |
| CD | ||||
| At least one diagnosis of CD Female Male |
61 38 23 |
31 23 8 |
– – – |
0.51 (0.38–0.64) 0.61 (0.43–0.76) 0.35 (0.16–0.57) |
| At least 2 diagnoses of CD | 37 | 24 | 7 | 0.65 (0.48–0.80) |
| At least 3 diagnoses of CD Female Male |
28 18 10 |
21 15 6 |
10 8 2 |
0.75 (0.55–0.89) 0.83 (0.59–0.96) 0.60 (0.26–0.88) |
| UC | ||||
| At least one diagnosis of UC Female Male |
216 118 98 |
117 47 70 |
– – – |
0.54 (0.47–0.61) 0.40 (0.31–0.49) 0.71 (0.61–0.80) |
| At least 2 diagnoses of UC | 124 | 91 | 26 | 0.73 (0.65–0.81) |
| At least 3 diagnoses of UC Female Male |
74 27 47 |
65 20 45 |
52 27 25 |
0.88 (0.78–0.94) 0.74 (0.54–0.89) 0.96 (0.86–0.99) |
Notes: a Using patients with a diagnosis of CD, UC, IBDu and MC in the patient records as cases. b Using patients with a diagnosis of CD, UC and IBDu in the records as cases.
Abbreviations: IBD, inflammatory bowel disease; CD, Crohn’s disease; UC, ulcerative colitis; NPR, the Danish National Patient Registry; IBDu, undifferentiated IBD; MC, microscopic colitis; PPV, positive predictive value; CI, confidence interval.