NPPB and hand, foot and mouth disease: Here, we studied potential indexes for the early diagnosis of severe HFMD and showed that the serum BNP level combined with other HFMD symptoms could be a biochemical indicator for complications (BNP >8.4 pmol/L), critical disease (BNP >38.8 pmol/L), and death (BNP >41.1 pmol/L) HFMD patients.