Table 2.
Primary Care Probabilistic Differential Diagnosis for Inhalation Anthrax
| Diagnoses (ICD-9 Code) | Responses No. (%) | Cumulative Percentage |
| 1. Pneumonia (480-486) | 237 (42.4) | 42.4 |
| 2. Influenza (487) | 56 (10.0) | 52.4 |
| 3. Viral syndrome (079.99) | 48 (8.6) | 61.0 |
| 4. Septicemia (038) | 43 (7.7) | 68.7 |
| 5. Bronchitis (466) | 41 (7.3) | 76.0 |
| 6. CNS infection (047-049, 320-323) | 35 (6.3) | 82.3 |
| 7. Gastroenteritis (008-009) | 21 (3.8) | 86.1 |
| 8. Upper respiratory tract infection (460, 465) | 17 (3.0) | 89.1 |
| 9. Nonspecific febrile illness (780.9) | 10 (1.8) | 90.9 |
| 10. Chronic obstructive pulmonary disease (496) | 8 (1.4) | 92.3 |
| 11. Congestive heart failure (428.0) | 7 (1.3) | 93.6 |
| 12. Pulmonary embolism (415.1) | 5 (0.9) | 94.5 |
| 13. Tuberculosis (011.0-011.9) | 4 (0.7) | 95.2 |
| 14. Sinusitis (461.0-461.9) | 2 (0.4) | 95.6 |
| 15. Dehydration (276.0-276.5) | 2 (0.4) | 95.9 |
| 16. Syncopal episode (780.2) | 2 (0.4) | 96.3 |
| 17. Hantavirus pulmonary syndrome (480.8) | 2 (0.4) | 96.6 |
| 18. Adult respiratory distress syndrome (518.5) | 2 (0.4) | 97.0 |
| 19. Dementia (294.1) | 1 (0.2) | 97.2 |
| 20. Acute multiple sclerosis (340) | 1 (0.2) | 97.4 |
| 21. Pyelonephritis (590.1) | 1 (0.2) | 97.6 |
| 22. Diabetic ketoacidosis (250.1) | 1 (0.2) | 97.7 |
| 23. Angina (413.0-413.9) | 1 (0.2) | 97.9 |
| 24. Coxsackie virus infection (074.0-074.8) | 1 (0.2) | 98.1 |
| 25. Pleurisy (511.0-511.9) | 1 (0.2) | 98.3 |
| 26. Lyme disease (088.81) | 1 (0.2) | 98.5 |
| 27. Leukocytosis (288.8) | 1 (0.2) | 98.7 |
| 28. Interstitial pneumonitis (515) | 1 (0.2) | 98.8 |
| 29. Mononucleosis (075) | 1 (0.2) | 99.0 |
| 30. Pericarditis (420.0-420.99) | 1 (0.2) | 99.2 |
| 31. Empyema (510) | 1 (0.2) | 99.4 |
| 32. Aortic dissection (441.0-441.9) | 1 (0.2) | 99.6 |
| 33. Plague (Yersinia pestis) (020.0-020.9) | 1 (0.2) | 99.7 |
| 34. Tularemia (021.0-021.8) | 1 (0.2) | 99.9 |
| 35. Intestinal perforation (569.83) | 1 (0.2) | 100.0 |
| Total | 559 (100) |
Note: Of the nonanthrax diagnoses, 559 were from inhalational anthrax cases, 52 from Legionella cases, and 105 from the influenza cases.
ICD-9 = International Classification of Diseases, 9th Revision; CNS = central nervous system.