Laboratory findings
Of 7 studies reporting data on blood tests, lymphocyte count was revealed in all 7 studies[15, 17, 18, 22, 23, 26, 27]. With pooled WMD of -0.42 (95 % CI: -0.64 to -0.20), it was revealed that severe Covid-19 case was more likely to have decreased lymphocyte count when compared with non-severe case (P=0.0002). However, no significant difference was found in leucocytes[15, 17, 22, 23, 27], neutrophils[15, 17, 22, 23, 26, 27] and monocyte count[15, 17, 27]. The outcome was explicitly expressed in Table 2.