187138 A comparative study of fluorescence microscopy and Ziehl-Neelsen techniques in the examination of sputum for the diagnosis of tuberculosis at a middle-income country referral hospital

Wednesday, October 29, 2008

Raul Chuquiyauri, MD , Graduate School Public Health, UCSD / SDSU, San Diego, CA
Armand Van Deun , Mycobacteriology Unit, Institute of Tropical Medicine, Antwerp, Belgium
Gabriela Torrea , Mycobacteriology Unit, Institute of Tropical Medicine, Antwerp, Belgium
Juan C. Agapito , Laboratorio de Mycobacteriologia, Hospital Nacional Cayetano Heredia, Lima, Peru
Eduardo Gotuzzo, MD, Dr , Institute of Tropical Medicine Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru
Kristien Verdonck, MD , Institute of Tropical Medicine Alexander von Humbolt, Universidad Peruana Cayetano Heredia, Lima, Peru
SETTING: Tuberculosis Reference Laboratory in Cayetano Heredia National Hospital in Lima, Peru. OBJECTIVES: Comparison of auramine fluorescence (FM) and Ziehl-Neelsen (ZN) light microscopy for diagnosis of tuberculosis.

MATERIAL & METHODS: Two direct smears from 2179 sputum specimens from patients with suspected pulmonary tuberculosis were prepared for blinded examination of one smear each by ZN and FM, with Lowenstein-Jensen (LJ) culture as gold standard.

RESULTS: 51 (2.3%) samples were excluded from analysis because of contaminated culture. All excluded samples were negative in both smears. Of the remaining 2 128 specimens, 272 (12.8%) were positive on culture and 151 (7.1%) were positive on at least one microscopic examination. ZN and FM detected 36.0% and 38.6% of 272 LJ culture-positive specimens. Patient-wise there were 8.1% (126 / 1 553) positives on any smear against 12.0% (187 / 1 553) on any culture. ZN and FM smear were positive in respectively 43.3% and 46.5% of culture-proven cases. All differences between microscopy and culture were significant (P<0.001), but not those between microscopy techniques. The considerable numbers of bacilli found in positive direct smears from discordant microscopy sets suggest that repeating smears can improve microscopy sensitivity more than variations of correctly executed technique, provided that overload is avoided. Since FM has the added advantage of being time-saving allowing a large number of sputum specimens to be examined in a given time then it could be particularly useful in laboratories handling large numbers of sputum specimens and could avoid the sensitivity loss associated with high workload.

Learning Objectives:
- Compare smear staining techniques for diagnosis of pulmonary tuberculosis. - Prioritize fluorescense microscopy techniques for high workload laboratories. - Discuss in which scenario the outcomes should be implemented.

Keywords: Tuberculosis, Developing Countries

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: I am a medical investigator and have been working on research the last 4 years on infectious diseases such as Tuberculosis, Malaria and Leptospirosis
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.