BACKGROUND Automated hematology analyzer is widely used by clinical laboratories to examine blood cell counts and differential leukocyte counts. However, a microscopic examination of a well-prepared blood film is still necessary and useful in most cases. METHODS Two patients with severe disease were required complete blood counts (CBC) after admission at West China Second University Hospital in Southwest China. RESULTS A false "platelet clumps?" flag was generated by the automated hematology analyzer Sysmex XE-2100. However, when the well-prepared blood film was reviewed, there was echinocytosis rather than clumps of platelets. In addition, both patients had severe metabolic acidosis with arterial blood pH <7.00 and HCO3- <4 mmol/l. On day 2 of admission, the false platelet clumps flags were not presented in both cases. CONCLUSIONS Our further results suggested that the false platelet clumps had been flagged probably due to the influence of the extremely low blood pH. These two cases emphasized that a microscopic examination of a blood film was central to the morphology of blood cells. When the result of microscopic examination was abnormal, it was suggested that the physician should consider further testing to find underlying condition.