Loa loa is usually diagnosed by the finding of microfilaria in peripheral blood smears or adults in the subconjunctiva. The blood films may be thick or thin and stained with Giemsa or hematoxylin-and-eosin. For increased sensitivity, concentration techniques can be used. These include centrifugation of the blood sample lysed in 2% formalin (Knott's technique), or filtration through a Nucleopore® membrane. Microfilariae of L. loa exhibit diurnal periodicity and a diagnosis is best made from blood collected during the mid-day (10 AM-2 PM). The presence of Calabar swellings can aid in the diagnosis.