Reasons for false-positive lipoarabinomannan ELISA results in a Tanzanian population

Inge Kroidl*ab, Petra Clowesb, Joshua Mwakyelub, Leonard Mabokob, Abubakary Kiangic, Andrea Rachowabd, Klaus Reitherbe, Jutta Jungb, Anthony Nsojob, Elmar Saathoffabd & Michael Hoelscherabda From the Division of Infectious Diseases and Tropical Medicine, Medical Centre of the University of Munich, Munich, Germanyb NIMR – Mbeya Medical Research Centre, Mbeya, Tanzaniac Mbeya Referral Hospital Laboratory, Mbeya, Tanzaniad German Centre for Infection Research (DZIF), Partnersite Munich, Germanye Swiss Tropical and Public Health Institute, Basel, SwitzerlandCorrespondence: I. Kroidl, Division of Infectious Diseases and Tropical Medicine, Medical Centre of the University of Munich (LMU), Leopoldstrasse 5, 80802 Munich, Germany. Tel: + 49 89 2180 17601. Fax: + 49 89 336038. E-mail: ikroidl@lrz.uni-muenchen.deAbstractLipoarabinomannan (LAM), a cell wall component of mycobacteria, can be detected in the urine of tuberculosis (TB) patients. Advantages of this diagnostic include the ease of sample collection and test methods. However, as with most new TB diagnostics, LAM tests have been evaluated in well-controlled laboratory settings and subsequently need assessment under real working conditions. Our experience showed that the diagnosis of TB using the detection of LAM in urine under field conditions is prone to false-positive results due to contamination. Dust and soil, but also stool, seemed to lead to increased OD values and thus false-positive results of the enzyme-linked immunosorbent assay (ELISA) for LAM; however, contamination with blood, as well as bacterial or fungal organisms, had no influence. The collection of urine for the detection of LAM should therefore follow strict collection criteria in order to avoid contamination.