ABSTRACT
<p><b>OBJECTIVE</b>To detect the anti-enterovirus 71 (EV71) IgM level in cerebrospinal fluid (CSF) of children with severe hand, foot and mouth disease (HFMD) induced by EV71 and then analyze the relationships among the IgM antibody levels, CSF routine examination and patients' clinical features, and thus to evaluate the clinical significance of anti-EV71 IgM as a new indicator for early diagnosis of children with severe HFMD induced by EV71.</p><p><b>METHOD</b>A total of 294 laboratory-confirmed cases of children with severe HFMD infected with EV71 were enrolled into the research group from March 2014 to June 2014, consisting of 53 fatal cases and 241 severe cases, and their CSF samples underwent enzyme-linked immunosorbent assay (ELISA) for anti-EV71 IgM levels, CSF routine and biochemical tests. Forty-one cases of children with severe HFMD induced by other enteroviruses were collected as antibody-testing control group during the same period.</p><p><b>RESULT</b>In the research group, the total positive rate of anti-EV71 IgM in 294 CSF samples of children with severe HFMD infected by EV71 was 60.2% (177/294); the positive rate of anti-EV71 IgM in the fatal HFMD subgroup was 62.3% (33/53); the positive rate of anti-EV71 IgM in the severe HFMD subgroup was 59.8% (144/241). In the control group, the results of CSF anti-EV71 IgM tests were all negative (0/41). In the research group, patients in antibody-positive subgroup (2.5±1.2) years old were younger than those in antibody-negative subgroup (2.9±1.1) years old (t=2.595, P=0.010). And within the antibody-positive subgroup, the patients ((1.9±0.7) years old) with fatal type disease were younger than those ((2.6±1.2) years old) with severe type disease (t=3.150, P=0.002). The CSF nucleated cells count and positive rates (105 (56,180) ×10(6) /L; 97.7% (173/177)) in antibody-positive subgroup were higher than those (62(30,150) ×10(6) /L; 83.8% (98/117)) in antibody-negative subgroup (Z=3.663, P=0.000; χ(2)=19.089, P=0.000). In antibody-positive subgroup, the percentage of monocytes (57±25)% was higher than that of polykaryocytes (43±25)%. In antibody-negative subgroup, the percentage of monocytes (50±26)% was close to that of polykaryocytes (50±26)%. In the antibody-positive subgroup, the ratio of the patients with nucleated cells count higher than 100×10(6)/L in fatal type group and severe type group was 69.7% (23/33) and 47.2% (68/144) respectively (χ(2)=5.429, P=0.02). The CSF protein quantity and positive rates in antibody-positive subgroup were higher than those in antibody-negative subgroup (Z=2.158, P=0.031; χ(2)=5.921, P=0.015).</p><p><b>CONCLUSIONS</b>The anti-EV71 IgM levels in CSF can serve as an important indicator for early diagnosis of children with severe HFMD induced by EV71. And the anti-EV71 IgM levels in CSF correlated to the CSF nucleated cells count and classification and CSF protein quantity. In the antibody-positive subgroup, the higher the nucleated cell count or the younger the age, the higher the possibility of patients to develop into fatal cases.</p>