Clinicoradiologic correlation in adult patients diagnosed with novel influenza A (H1N1)

Background: Influenza A(H1N1) infection affected Indian population in 2009. Patients needed ICU admission and monitoring. Objectives: To describe and correlate clinical and radiographic features of Influenza A(H1N1) infection in patients hospitalised in Intensive care unit. Material and Methods: Retrospective study of records of 100 RT-PCR confirmed patients with Influenza A(H1N1) infection from August 2009 to March 2010 was done. Each patient underwent an evaluation to determine clinical and radiographic features. Results: Mean age of the patients was 33.43 years (±12.152) with maximum patients between 18-40 years, with 53% males and 43% females. Cough(96%), Fever (95%), breathlessness (83%), throat pain (34%), crepitations (69%), Tachypnoea (59%)were the prominent symptoms and signs. 61%(n=63) had comorbid condition like pregnancy (n=13,20.63%), Diabetes Mellitus (DM) (n=12,19.05%), HT (n=11,17.60%), Obesity (n=10, 15.87%) and Rheumatic Valvular Heart Disease (RVHD) (n=6,09.52%). Chest X ray was abnormal in 91% patients and normal in 09% pts. Bilateral findings were seen in 61.53% cases. Most common zones affected were lower zones (77.46%), then middle zones (71.42%), followed by upper zones (42.7%). Most common patterns were consolidation (64.83%), reticulonodular (24.17%) and nodular (10.98%). 27.47% had two, 21.97% had four, 19.78 % had three,12.08% had six, 7.69% had five and10.98% had single zone involvement. Fever, cough and tachypnoea were present in all 100% pts with nodular pattern while crepitations were observed in 79.66% cases of consolidation. Patchy consolidation was seen in comorbidities like pregnancy (n=10) and obesity (n=06), while reticulonodular pattern was observed in hypertensive patients (n=06). Maximum number of deaths were between 21 and 30 years of age (60.71 %). Total number of deaths were 28 with 60.71% (n=17) deaths between 21 and 30 years of age. Deaths were more in presence of comorbidities like Pregnancy (n=5, 17.85%), Hypertension (n=4,14.28%), Diabetes (n=3 10.21%) and RVHD (n=3,10.71%), in presence of RLZ involvement (92.85%), RMZ (89.28%), LMZ (85.21%) and RUZ involvement (71.42%), with consolidation pattern (57.14%) followed by reticulonodular pattern (21.42%) and in presence of six zone involvement (36.37%) followed by four zone (35%) and then by three(33%) and two (32%) zone involvement. Mean duration of hospital stay was 9.1 days. 23% patients stayed for less than 5 days, 41% stayed between 9 and 14 days while only 7% required to stay for more than 15 days. 37% pts showed normal Xray at the time of discharge or death. 38% patients showed persistence of radiological lesion at discharge or death. Conclusions: Young to middle age patients were commonly affected. Common comorbidities were Pregnancy, Diabetes, Hypertension, and Obesity and patients had fever, cough, breathlessness, tachypnoea, crepitations as common clinical features. Radiologically it was multizonal, bilateral disease with predominant lower zone involvement and common patterns were consolidation followed by reticulonodular and nodular. Patchy consolidation was more common in pregnancy and obesity while reticulonodular pattern was more in hypertensive patients. Fever, cough and tachypnoea were present in all 100% pts with nodular pattern. Crepitations were common in pts with consolidation. Clinical recovery preceded radiological recovery. Young to middle aged individuals died more. Deaths were more in presence of comorbidities like Pregnancy, HT, DM and RVHD, also with RLZ, RMZ, LMZ involvement and with consolidation pattern and with six zone involvement.