Prevalence of Cytopenia and Evaluation of Its Clinical Significance in Children with influenza A(H1N1)

Aim: Although influenza A causes flu epidemics every year, in 2009 the virus named influenza A H1N1 caused a pandemic. Mortality rates were reported higher than expected due to secondary infections. The aim of this study is to evaluate cytopenia which is one of the hematologic complications in patients who present with flu symptoms and are positive for influenza A H1N1.
Method: 503 patients presenting at our Pediatrics Clinic with flu symptoms in November and December 2009 were retrospectively analyzed for epidemiologic and hematologic findings. The diagnosis of H1N1 was made with antigen tests studied on the nasopharyngeal swab.
Result: 269 cases were male and 234 were female. Mean age of the patients was 8.8 years (six months- 17 years). 149 of 503 cases (29.6%) were positive for influenza A and 354 cases (70.4%) were negative. Sixty-three (42%) of positive cases underwent full blood count. Nine (14.3%) of these had leucopenia, 12 (19%) had neutropenia and 10 (15.9%) had lymphopenia. Hemogram was performed on 120 cases who were negative for influenza A. Only three (2.5%) of these had leucopenia, 2 cases (1.7%) had neutropenia and 1 case (0.8%) had lymphopenia. The difference between the groups was statistically significant (p<0.004, p<0.001, p<0.001). None of the cases had anemia or thrombocytopenia. Cytopenia resolved in the follow-up with the disappearance of symptoms and there was no permanent morbidity in any of the cases.
Conclusion: Influenza A H1N1 infection leads to leucopenia but does not cause permanent cytopenia.