The biggest pitfall in most laboratories in developed countries is leaving too great a delay between taking the blood sample and making the blood films. As blood cools to room temperature, male gametocytes will divide and release microgametes: these are long sinuous filamentous structures that can be mistaken for organisms such as "Borrelia". If the blood is kept at warmer temperatures, will rupture and merozoites invading erythrocytes will mistakenly give the appearance of the accolé form of "P. falciparum". If "P. vivax" or "P. ovale" is left for several hours in EDTA, the buildup of acid in the sample will cause the parasitised erythrocytes to shrink and the parasite will roll up, simulating the appearance of "P. malariae". This problem is made worse if anticoagulants such as heparin or citrate are used. The anticoagulant that causes the least problems is EDTA. Romanowsky stain or a variant stain is usually used. Some laboratories mistakenly use the same staining pH as they do for routine haematology blood films (pH 6.8): malaria blood films must be stained at pH 7.2, or Schüffner's dots and James' dots will not be seen.