Validity of ICD-10 codes for hyponatraemia recorded in the DNRP, stratified by age group categories, year and department of admission, for serum sodium values <135* and <125 mmol/L†
| Sensitivity, % (95% CI) | Specificity, % (95% CI) | PPV, % (95% CI) | NPV % (95% CI) | |||||
|---|---|---|---|---|---|---|---|---|
| <135 mmol/L | <125 mmol/L | <135 mmol/L | <125 mmol/L | <135 mmol/L | <125 mmol/L | <135 mmol/L | <125 mmol/L | |
| Age, years | ||||||||
| <15 | 0.2 (0.1 to 0.2) | 3.0 (1.5 to 5.2) | 100 (100 to 100) | 100 (100 to 100) | 84.4 (67.2 to 94.7) | 34.4 (18.6 to 53.2) | 94.6 (94.6 to 94.7) | 99.9 (99.9 to 99.9) |
| 15–34 | 0.2 (0.2 to 0.3) | 4.7 (3.0 to 6.9) | 100 (100 to 100) | 100 (100 to 100) | 80.0 (65.4 to 90.4) | 51.1 (35.8 to 66.3) | 95.5 (95.4 to 95.5) | 99.9 (99.9 to 99.9) |
| 35–49 | 0.9 (0.8 to 1.0) | 7.8 (6.7 to 9.0) | 100 (100 to 100) | 100 (100 to 100) | 91.3 (87.3 to 94.4) | 67.2 (61.2 to 72.8) | 90.8 (90.7 to 90.9) | 99.3 (99.3 to 99.3) |
| 50–64 | 1.3 (1.3 to 1.4) | 9.6 (8.9 to 10.3) | 100 (100 to 100) | 99.9 (99.9 to 99.9) | 93.9 (92.2 to 95.3) | 69.6 (66.7 to 72.3) | 83.6 (83.5 to 83.7) | 98.5 (98.4 to 98.5) |
| 65–79 | 1.8 (1.7 to 1.9) | 13.6 (12.9 to 14.4) | 100 (100 to 100) | 99.8 (99.8 to 99.8) | 92.9 (91.7 to 94.0) | 57.2 (55.0 to 59.3) | 79.1 (78.9 to 79.2) | 98.5 (98.4 to 98.5) |
| ≥80 | 3.4 (3.3 to 3.6) | 21.0 (19.9 to 22.1) | 99.9 (99.9 to 99.9) | 99.5 (99.5 to 99.5) | 92.0 (90.8 to 93.0) | 47.7 (45.7 to 49.7) | 75.7 (75.5 to 75.9) | 98.3 (98.3 to 98.4) |
| Admission year | ||||||||
| 2006 | 1.5 (1.4 to 1.7) | 12.5 (11.5 to 13.5) | 100 (100 to 100) | 99.9 (99.9 to 99.9) | 92.8 (90.8 to 94.5) | 66.6 (63.2 to 69.9) | 86.8 (86.6 to 86.9) | 99.0 (98.9 to 99.0) |
| 2007 | 1.4 (1.3 to 1.5) | 12.0 (11.0 to 13.1) | 100 (100 to 100) | 99.9 (99.9 to 99.9) | 94.4 (92.4 to 96.0) | 65.3 (61.6 to 68.8) | 87.0 (86.9 to 87.1) | 99.0 (99.0 to 99.1) |
| 2008 | 1.7 (1.6 to 1.8) | 12.3 (11.3 to 13.3) | 100 (100 to 100) | 99.9 (99.9 to 99.9) | 91.1 (89.1 to 92.8) | 53.6 (50.4 to 56.8) | 85.9 (85.8 to 86.1) | 99.0 (98.9 to 99.0) |
| 2009 | 1.8 (1.7 to 1.9) | 12.6 (11.6 to 13.6) | 100 (100 to 100) | 99.9 (99.8 to 99.9) | 93.4 (91.7 to 94.8) | 51.4 (48.4 to 54.5) | 85.5 (85.3 to 85.6) | 99.0 (98.9 to 99.0) |
| 2010 | 1.9 (1.8 to 2.0) | 14.2 (13.2 to 15.4) | 100 (100 to 100) | 99.9 (99.9 to 99.9) | 91.6 (89.8 to 93.2) | 54.4 (51.4 to 57.4) | 86.3 (86.2 to 86.4) | 99.1 (99.0 to 99.1) |
| 2011 | 2.2 (2.0 to 2.3) | 15.2 (14.1 to 16.4) | 100 (100 to 100) | 99.9 (99.9 to 99.9) | 92.2 (90.6 to 93.6) | 49.8 (47.0 to 52.7) | 85.8 (85.7 to 85.9) | 99.1 (99.0 to 99.1) |
| Department | ||||||||
| Internal medicine | 2.7 (2.7 to 2.8) | 16.5 (16.0 to 17.0) | 99.9 (99.9 to 100) | 99.7 (99.7 to 99.7) | 92.8 (92.1 to 93.4) | 56.0 (54.7 to 57.3) | 80.3 (80.2 to 80.4) | 98.3 (98.3 to 98.3) |
| Surgical | 0.2 (0.2 to 0.2) | 2.3 (1.9 to 2.8) | 100 (100 to 100) | 100 (100 to 100) | 90.6 (85.8 to 94.3) | 57.6 (50.5 to 64.5) | 86.0 (85.9 to 86.1) | 99.2 (99.2 to 99.2) |
| Gynaecological/obstetric | 0.1 (0.1 to 0.3) | 3.1 (1.2 to 6.7) | 100 (100 to 100) | 100 (100 to 100) | 76.9 (46.2 to 95.0) | 46.2 (19.2 to 74.9) | 98.0 (97.9 to 98.0) | 99.9 (99.9 to 100) |
| Paediatric | 0.2 (0.1 to 0.3) | 3.4 (1.7 to 5.8) | 100 (100 to 100) | 100 (100 to 100) | 85.3 (68.9 to 95.0) | 35.3 (19.7 to 53.5) | 90.4 (90.3 to 90.6) | 99.8 (99.8 to 99.8) |
| Other | 0.3 (0.2 to 0.5) | 1.5 (0.4 to 3.9) | 100 (100 to 100) | 100 (100 to 100) | 58.3 (36.6 to 77.9) | 16.7 (4.74 to 37.4) | 95.2 (95.0 to 95.3) | 99.7 (99.7 to 99.8) |
*Corresponding to <133 mmol/L for infants ≤30 days of age.
†Corresponding to <123 mmol/L for infants ≤30 days of age.
DNRP, Danish National Registry of Patients; ICD-10, International Classification of Diseases, 10th revision; NPV, negative predictive value; PPV, positive predictive value.