Intraerythrocytic haem acts as a pseudoperoxidase and can be quantified with a chromogenic substrate. A) Lysed P. falciparum-infected erythrocytes oxidize the chromogenic substrate TMB. There is a strong correlation between the OD-value and number of lysed iRBC (r2 = 0.98, p <0.001). B) The chromogenic signals generated from lysates of known numbers of erythrocytes and infected erythrocytes from different conditions were compared 1 min after addition of TMB. No statistical difference was observed between erythrocyte populations (p >0.7). See text for details. C) When the haem-driven reaction was continued 11 min the signal decreased in wells with the highest numbers of erythrocytes and increased in wells with low number of erythrocytes. On all graphs, symbols represent mean values and error bars show standard deviation.