Significance of sputum cultures in diagnosis of invasive pulmonary aspergillosis in acute leukemia ? A meta analysis

The diagnosis of Invasive Pulmonary Aspergillosis (IPA) and therapy with Amphotericin B appear to improve survival, but the early diagnosis is difficult. There are no pathognomonic clinical findings for IPA. The commonest presentation is compatible with any of bacterial, fungal, viral or protozoan infections. In addition, IPA may coexist with or arise during the therapy of other infections in immune compromised patients. It was thought that ante mortem isolation of Aspergillus species from respiratory secretions in pathologically confirmed cases occur infrequently. Demonstration of tissue invasion by fungal hyphae remained the accepted standard for diagnosis of IPA. Sputum culture is regarded as not useful for the diagnosis of IPA. Colonization of aspergillus may occur without invasion, hence, culture of respiratory secretions were not reliable. Aggressive diagnostic methods to establish the diagnosis of IPA are warranted. However there may exist important subsets of patients where sputum culture of Aspergillus may still be diagnostically useful. The underlying disease, i.e. immune suppression, neutropenia/ leukemia is a critical factor in selecting patients where sputum cultures may be useful. The degree of immune suppression increases, the diagnostic specificity of isolation of aspergillus from sputum. In this article, a meta analysis of 21 studies, spanning 27 years, the methods adopted for diagnosing IPA by various authors is analysed and discussed. The detailed pathogenesis of IPA is also discussed.