Tuesday, October 4, 2011

A central TB diagnostic lab

I spent the past two days on a computer at the National Health Laboratory Service’s TB lab in Cape Town, finding codes and dates needed to link sputum samples to clinical data for a cohort I’m studying of MDR TB patients from a nearby farming region.  The South African government somehow has decided to keep this NHLS facility occupying prime downtown real estate – next door is historic Somerset hospital, and over lunch, I walked a couple of blocks to the high-end waterfront shopping mall – but inside, it’s a giant sample-processing factory.  Assembly lines of slides and stains and culture bottles, overflowing boxes of discarded samples making room for a new day’s sputa, a room of Bactec machines, new machines for rapid drug sensitivity testing, all kept running from early morning to 11pm, with two shifts of workers each day.  I made the mistake of trying to look up a sample by date, not realizing that a new one is logged about every two minutes.  And repetition makes the work efficient; this may seem silly, but I was amazed by how quickly the woman working next to me could stack up a tabletop array of glass slides that were lying side by side (15 or 20 per second, maybe? I’m not exaggerating - it was impressive.)

The high volume and necessarily rapid turnover mean it’s impossible to go back and find mycobacterial samples of interest after the fact.  But fortunately, our collaborators at Stellenbosch University have set up a system where all multidrug resistant samples automatically get sent to them for cataloguing, storage, and further typing and molecular analysis.  I’m eager to link their molecular data with the clinical data we’ve collected these past few weeks and see what we find.  Also curious to see whether we can show any effect from the recent implementation of rapid PCR diagnostics: Shorter times to reporting MDR TB? Shorter times to getting patients on appropriate treatment? Or, a longer shot but the real interesting question, less transmission in the community?

Emily Kendall, MGH, PGY-2 Internal Medicine