Here is one study from a quick search on PubMed

Tim Morken,
CDC, Atlanta

  
Historical risks of tuberculin skin test conversion among non-physician
staff at a large urban hospital.
Am J Ind Med 2002 Sep;42(3):228-35  
Miller AK, Tepper A, Sieber K.

Division of Surveillance, Hazard Evaluations and Field Studies, National
Institute for Occupational Safety and Health, Centers for Disease Control
and Prevention, Cincinnati, Ohio, USA. amiller@hrsa.gov

BACKGROUND: Nosocomial transmission of Mycobacterium tuberculosis among
workers at a 1000-bed inner-city hospital led to an extensive evaluation of
this risk among workers with potential exposure to TB patients or laboratory
specimens. METHODS: Retrospective cohort study to determine the incidence
and risk of tuberculin skin test (TST) conversions among workers employed
1/1/90 to 9/30/92. RESULTS: Personal, community, and occupational risk
factors were evaluated in 2,362 workers with potential M. tuberculosis
exposure and 886 workers with no known exposure. The 33-month cumulative
rate of TST conversion was 5.8% for potentially exposed workers and 2.0% for
controls (RR 3.6; 95% CI; 2.2-5.8). Among workers with potential M.
tuberculosis exposure, statistically significantly elevated risks were found
for nurses, laboratory technicians, pharmacy workers, phlebotomists,
housekeepers, clerks, emergency room workers, and emergency responders.
CONCLUSIONS: Workers with patient contact and those employed in certain
occupational groups were at increased risk for occupational M. tuberculosis
infection. Published 2002 Wiley-Liss, Inc.

PMID: 12210691 [PubMed - indexed for MEDLINE] 

-----Original Message-----
From: Jasper, Thomas [mailto:TJasper@smdc.org]
Sent: Thursday, October 17, 2002 2:01 PM
To: 'histonet@pathology.swmed.edu'
Subject: TB Exposures


My fellow histonetters,

I would like to inquire about TB exposures.  This would apply to histotechs,
PAs, pathologists, autopsy techs or any other lab personnel working in
anatomic pathology.  Specifically, how many with a prior negative PPD
converted to a positive PPD after exposure to a known case?  Demographics
will factor into this inquiry so if you choose to respond it would be
helpful to know where you're from.  I do not wish to clog the net with
responses, but others on this list may have interest in this data.  
Thanks!   


Thomas Jasper HT(ASCP)BAS
Anatomic Pathology Coordinator
SMDC Clinical Laboratory
Duluth, MN
tjasper@smdc.org