Peripheral Blood Film Examination In Malawi: The Maximum Diagnostic Information for the Least Resources?.

Malawi is the 23^th least developed country according to the 2009 UN human development index and has a per capita health expenditure of $17 per year. In common with most of sub-Saharan Africa, severe haematological abnormalities are common in hospital patients, both contributing to ill health and reflecting the nature of underlying illnesses. Facilities for investigating abnormal results are limited and there are chronic problems with supply and maintenance of equipment and reagents. Examination of peripheral blood films provides extensive diagnostic information and can be performed with equipment routinely available even in district laboratories but there are few data on the feasibility and utility of routine blood film examination in this setting.

Routine preparation of thin blood films stained with reverse Field's stain was introduced as a laboratory standard operating procedure for all FBC results meeting predetermined criteria [Hb<7.0 or >16.5 g/dl; MCV<60 or>100 fl; WBC <3.5 or >17.0 ×10⁹/L; PLT <70 or >650 ×10⁹/L] in the major teaching hospital. Films were reported by an experienced haematologist. Handwritten laboratory records of FBC and blood film reports over a 12 month period were reviewed retrospectively.

From 35449 FBC samples received 9543(26.9%) met criteria for film preparation. 3745 (39.2% of samples meeting criteria) were prepared. The proportion of films made improved during the study period; films were less likely to be prepared at weekends or late in the day. High day-to-day variability suggests that compliance levels may reflect staff on duty on individual days; workload on a given day did not appear negatively correlated with compliance. 69.5% of film reports gave added diagnostic information (other than simply confirming automated counts); many of the features found were not evident from the patient's clinical condition. Important findings included 33 new cases of leukaemia (14 acute leukemia, 6 CML and 13 CLL or other lymphoid disorders). 6.5% of films showed features suggesting haemolysis or increased red cell production. 2.2% showed specific features (not just macrocytosis) suggesting megaloblastic anaemia, 4.7% showed malaria parasites or other evidence of malaria such as pigment. 2.5% of films showed features raising the possibility of error in the automated counts. Reactive features were very common (57% of films). The 10 most common classes of film findings [see table 1] accounted for 75.8% of informative blood film reports.

Routine peripheral blood film examination in a sub-Saharan African context provides a high yield of diagnostic information with minimal extra equipment requirement. A small number of common findings account for the majority of reports, suggesting that focussed training to identify these common abnormalities could have substantial benefits and could be implemented in a brief training programme. The variable compliance with the standard operating procedure suggests that staff confidence and enthusiasm may be the most important barriers to the incorporation of film reporting into routine practice.

No relevant conflicts of interest to declare.