Table 3.
Factors associated with influenza infection and tuberculosis-influenza co-infection compared with tuberculosis infection only in patients admitted with severe respiratory illness (acute and chronic) and tested for tuberculosis and influenza at four sites in South Africa, June 2010- December 2011
| Variables | Laboratory confirmed tuberculosis Reference a | Laboratory confirmed influenza | Laboratory confirmed tuberculosis-influenza co-infection | |||||
|---|---|---|---|---|---|---|---|---|
| n/N (%) | RRR b | ARRR c (95% CI) | n/N (%) | RRR b | ARRR c (95% CI) | |||
| Age group (years) | 0-4 | 47/423 (11) | 46/275 (10) | Reference | Reference | 8/34 (22) | Reference | Reference |
| 5-24 | 44/423 (10) | 28/275 (11) | 0.6 (0.3-1.2) | 1.3 (0.6-2.9) | 3/34 (9) | 0.4 (0.1-1.6) | 0.5 (0.1-2.5) | |
| 25-44 | 231/423 (55) | 121/275 (44) | 0.5 (0.3-0.8) | 1.5 (0.8-2.8) | 18/34 (53) | 0.5 (0.2-1.2) | 0.5 (0.2-1.7) | |
| 45-64 | 86/423 (20) | 57/275 (21) | 0.7 (0.4-1.1) | 1.3 (0.7-2.5) | 4/34 (12) | 0.3 (0.1-0.9) | 0.3 (0.1-2.5) | |
| 65+ | 15/423 (3) | 23/275 (8) | 1.6 (0.7-3.4) | 3.9 (1.6-9.8) | 1/34 (3) | 0.3 (0.04-3.4) | 9.53e-07 | |
| Sex | Female | 247/423 (58) | 176/275 (64) | Reference | 20/34 (59) | Reference | ||
| Male | 176/176 (42) | 99/275 (36) | 0.8 (0.6-1.1) | 14/34 (41) | 1.0 (0.5-1.9) | |||
| Site | Chris Hani Baragwanath | 124/423 (29) | 169/275 (61) | Reference | 17/34 (50) | Reference | ||
| Mapulaneng & Matikwana | 21/423 (5) | 11/275 (4) | 0.4 (0.2-0.8) | 2/34 (6) | 0.7 (0.1-3.2) | |||
| Edendale | 48/423 (11) | 22/275 (8) | 0.3 (0.2-0.6) | 1/34 (3) | 0.2 (0.01-1.2) | |||
| Klerksdorp/Tshepong | 230/423 (54) | 73/275 (27) | 0.2 (0.2-0.3) | 14/34 (41) | 0.4 (0.2-0.9) | |||
| HIV status | Negative | 82/392 (21) | 99/257 (39) | Reference | Reference | 7/32 (22) | Reference | Reference |
| Positive | 310/392 (79) | 158/257 (61 | 0.4 (0.3-0.6) | 0.6 (0.4-0.9) | 25/32 (78) | 0.9 (0.4-2.3) | 1.6 (0.5-4.9) | |
| Underlying medical conditionsd | No | 394/423 (93) | 240/275 (87) | Reference | 32/34 (94) | Reference | ||
| Yes | 29/423 (7) | 35/275 (13) | 1.98 (1.2-3.3) | 2/34 (6) | 0.8 (0.2-3.7) | |||
| Duration of symptoms prior to admission | <7 | 166/412 (40) | 194/275 (71) | Reference | Reference | 24/33 (73) | Reference | Reference |
| ≥7 | 246/412 (60) | 81/275 (29) | 0.3 (0.2-0.4) | 0.4 (0.2-0.4) | 9/33 (27) | 0.3 (0.1-0.6) | 0.3 (0.1-0.7) | |
| Pneumoccocal co-infection on PCRe | No | 371/388 (96) | 233/246 (95) | Reference | Reference | 29/30 (97) | ||
| Yes | 17/388 (4) | 13/246 (5) | 1.2 (0.6-2.6) | 1/30 (3) | 0.8 (0.1-5.8) | |||
| Oxygen therapy | No | 313/423 (74) | 158/275 (57) | Reference | Reference | 24/34 (71) | Reference | Reference |
| Yes | 110/423 (26) | 117/275 (43) | 2.1 (1.5-2.9) | 1.9 (1.3-2.8) | 10/34 (29) | 1.2 (0.5-2.6) | 0.97 (0.4-2.3) | |
| Tuberculosis treatment | No | 185/422 (44) | 243/274 (89) | Reference | 20/34 (59) | Reference | ||
| Yes | 237/422 (56) | 31/274 (11) | 0.1 (0.1-0.2) | 14/34 (41) | 0.5 (0.3-1.1) | |||
| Hospital duration (days) | ≤ | 257/420 (61) | 198/274 (72) | Reference | 22/33 (67) | Reference | Reference | |
| >7 | 163/420 (39) | 76/274 (28) | 0.6 (0.4-0.8) | 0.6 (0.4-0.9) | 11/33 (33) | 0.8 (0.4-1.7) | 0.7 (0.3-1.5) | |
| Died | No | 391/422 (73) | 265/274 | Reference | Reference | 30/34 (88) | Reference | Reference |
| Yes | 31/422 (7) | 9/274 | 0.4 (0.2-0.9) | 0.5 (0.2-1.1) | 4/34 (12) | 1.7 (0.6-5.1) | 3.2 (1.1-10.0) | |
aTuberculosis only group used as reference for multinomial model analysis (i.e. comparing influenza only to tuberculosis only and tuberculosis–influenza co-infection to tuberculosis only group).
bUnadjusted relative risk ratio (RRR) at multivariable analysis.
cAdjusted relative risk ratio (ARRR) at multivariable analysis.
dUnderlying conditions included any of the following: Asthma, other chronic lung disease, chronic heart disease (valvular heart disease, coronary artery disease, or heart failure excluding hypertension), liver disease (cirrhosis or liver failure), renal disease (nephrotic syndrome, chronic renal failure), diabetes mellitus, immunocompromising conditions excluding HIV infection (organ transplant, immunosuppressive therapy, immunoglobulindeficiency, malignancy), neurological disease (cerebrovascular accident, spinal cord injury, seizures, neuromuscular conditions) or pregnancy. Comorbidities were considered absent in cases for which the medical records stated that the patient had no underlying medical condition or when there was no direct reference to that condition.
e lyt A PCR positive for Streptococcus pneumoniae on blood specimen.