Method

A blinded independent study was conducted on 143 sputum samples from the FIND sputum bank which had previously been tested by indirect microscopy and culture. 0.5 ml of each sputum was thinned using sodium hydroxide, extracted using TB-Beads (Microsens Medtech Ltd) and then tested using an antigen ELISA (constructed by Microsens Medtech Ltd). After testing the panel, the samples were unblinded. 

Results

Discussion

There was good correlation between the TB-Bead extraction and ELISA compared to indirect microscopy and culture. One of four of the ELISA false positive (i.e.smear negative and culture negative) samples when tested by PCR for mycobacteria was positive which demonstrates that the ELISA signal can detect true positives in the absence of microscopy or culture positive results.

We are working on conversion of the ELISA format to a 30 minute point of care (POC) format which can be used without specialist equipment. Preliminary results indicate that the POC format has similar sensitivity to the ELISA and we will present this data in a future Newsletter.

Acknowledgments:

Gerd Michel and Eloise Valli, FIND

Dr Harald Hoffmann and Evgeni Sahalchyk, Asklepios Fachkliniken München-Gauting, Academic Teaching Hospital, University of Munich

* * * * * * * * *

Diagnosis of tuberculosis from sputum by Microsens TB-Beads extraction followed by Microsens TB antigen ELISA

In this issue we demonstrate that the TB-Beads can be used to extract TB bacteria and TB antigens from sputum which can then be detected by ELISA.  The data was recently presented in the FIND symposium at the IUATLD meeting in Lille.

Consumption  November 2011/1

Towards a Point-of-Care and ELISA test for mycobacteria