Table 5.
Number of Control Patients Positive or Negative for Alpha-Gal sIgE Antibodies, by Tick Exposure and Environmental Characteristics
| Characteristic | sIgE+ controls, n (%) | sIgE− controls, n (%) | OR | LCL | UCL |
|---|---|---|---|---|---|
|
| |||||
| Tick exposure | |||||
| Found a tick on body in past year (or year before symptom onset) | 44 (70) | 46 (36) | 4.25 | 2.21 | 8.18 |
| No tick on body in past year (or year before symptom onset) | 18 (29) | 80 (63) | Ref | — | — |
| Unsure about finding a tick on body in past year | 1 (2) | 2 (2) | — | — | — |
| Number of times ticks were found in past year | |||||
| 10 or more | 8 (19) | 7 (16) | 1.54 | 0.50 | 4.25 |
| 7–9 | 2 (5) | 0 (0) | 6.70 | 0.65 | Inf |
| 4–6 | 10 (23) | 6 (14) | 2.25 | 0.73 | 6.90 |
| 1–3 | 23 (54) | 31 (71) | Ref | — | — |
| Number of ticks found biting or stuck on body | |||||
| 4 or more | 4 (6) | 4 (3) | 2.05 | 0.45 | 9.92 |
| 3 | 6 (10) | 0 (0) | 26.68 | 2.77 | Inf |
| 2 | 10 (16) | 10 (8) | 2.21 | 0.65 | 6.85 |
| 1 | 13 (21) | 12 (9) | 2.29 | 0.75 | 6.95 |
| 0 | 9 (14) | 19 (15) | Ref | — | — |
| Tick bite reaction | |||||
| Bites from a tick created a mark or took longer than usual to heal | 12 (19) | 8 (6) | 1.56 | 0.55 | 4.43 |
| Bites from a tick did not create a mark or take a long time to heal | 24 (38) | 25 (20) | Ref | — | — |
| Information about tick bite reaction not applicable or missing | 27 (43) | 95 (74) | — | — | — |
| Primary residence | |||||
| Apartment | 1 (2) | 10 (8) | 0.28 | 0.03 | 1.23 |
| Duplex | 1 (2) | 1 (1) | 1.94 | 0.20 | 19.10 |
| Townhome | 2 (3) | 2 (2) | 1.94 | 0.33 | 11.39 |
| Single family home | 59 (94) | 115 (90) | Ref | — | — |
| Amount of land around primary residence | |||||
| 5 or more acres | 22 (35) | 21 (16) | 6.64 | 2.36 | 18.55 |
| 2 to <5 acres | 16 (25) | 22 (17) | 4.61 | 1.59 | 13.20 |
| 1 to <2 acres | 11 (18) | 24 (19) | 2.90 | 0.97 | 8.66 |
| 0.5 to <1 acres | 6 (10) | 21 (16) | 1.81 | 0.54 | 6.11 |
| 0 to <0.5 acres | 6 (10) | 38 (30) | Ref | — | — |
| Not sure | 2 (3) | 2 (2) | — | — | — |
| Characteristics of land around primary residence | |||||
| Manicured grass lawn | 59 (94) | 118 (92) | 1.17 | 0.39 | 3.94 |
| No manicured grass lawn | 4 (6) | 10 (8) | Ref | — | — |
| Shrubs and brush | 51 (81) | 82 (64) | 2.38 | 1.16 | 4.88 |
| No shrubs and brush | 12 (19) | 46 (36) | Ref | — | — |
| Farmland | 18 (29) | 24 (19) | 1.73 | 0.86 | 3.49 |
| No farmland | 45 (71) | 104 (81) | Ref | — | — |
| Wooded forest | 60 (95) | 102 (80) | 4.47 | 1.56 | 16.50 |
| No wooded forest | 3 (5) | 26 (20) | Ref | — | — |
| Frequency of seeing deer near residence | |||||
| Monthly or less | 13 (21) | 42 (33) | 0.60 | 0.28 | 1.26 |
| Daily or weekly | 50 (79) | 86 (67) | Ref | — | — |
| Hours outside per week | |||||
| 25 or more | 17 (27) | 21 (16) | 2.49 | 1.04 | 5.96 |
| 19–24 | 6 (10) | 19 (15) | 0.97 | 0.33 | 2.86 |
| 13–18 | 10 (16) | 13 (10) | 2.36 | 0.86 | 6.51 |
| 7–12 | 16 (25) | 32 (25) | 1.54 | 0.66 | 3.57 |
| 0–6 | 14 (22) | 43 (34) | Ref | — | — |
| Hours outside per week in wooded areas | |||||
| 17 or more | 10 (16) | 10 (8) | 2.26 | 0.87 | 5.88 |
| 13–16 | 2 (3) | 9 (7) | 0.59 | 0.12 | 2.22 |
| 9–12 | 7 (11) | 14 (11) | 1.13 | 0.42 | 3.02 |
| 5–8 | 13 (21) | 25 (20) | 1.17 | 0.54 | 2.58 |
| 0–4 | 31 (49) | 70 (55) | Ref | — | — |
Abbreviations: Inf, infinity; LCL, lower confidence limit; OR, odds ratio; Ref, reference; sIgE, specific immunoglobulin E; UCL, upper confidence limit.