[1] Natl Univ Singapore Hosp, Dept Lab Med, Singapore, Singapore
[2] Univ Hosp Leicester NHS Trust, Leicester Royal Infirm, Leicester, Leics, England
[3] Univ Leicester, Dept Infect, Immun, Inflammat, Leicester, Leics, England
[4] Natl Univ Singapore, Yong Loo Lin Sch Med, Dept Pathol, 21 Lower Kent Ridge Rd, Singapore 119077, Singapore