Investigating recurrent respiratory infections in primary care.

a common cause for community acquired pneumonia, but recurrent infections are unusual in a young, healthy non-smoker. Thus repeated infections with these organisms should prompt investigations for possible underlying immunodeficiency. When evaluating patients with recurrent infection, use the acronym SPUR (severe, persistent, unusual, or recurrent) to prompt appropriate investigations for underlying causes. In this case scenario, chronic medical conditions such as diabetes or renal disease, which are associated with an increased tendency to recurrent infection, are effectively excluded by appropriate initial laboratory investigations. The clinical picture does not suggest immunodeficiency involving cellular immunity (most commonly resulting from infection with HIV), although a history of high risk sex or of misuse of intravenous drugs may indicate the need for screening. Secondary antibody deficiencies result most commonly from immunosuppression in lymphoid malignancy or more rarely from protein loss from either the renal or gastrointestinal tracts. Lymphoid malignancies should be considered but are unlikely in the absence of weight loss, fevers, lymphadenopathy, or splenomegaly and with a normal full blood count. The primary antibody deficiency syndromes are a group of rare disorders with a prevalence of around 1 in 50 000 which can present at any age and are characterised by the inability to produce clinically effective antibody responses to infection. With these disorders, delay in diagnosis remains a problem and contributes to chronic disease.2