Purchase this article with an account.
D. V. Vasconcelos-Santos, M. K. Ko, S. Saraswathy, N. A. Rao; Quantification of Mycobacterial Load in Patients With Suspected Ocular Tuberculosis in a Nonendemic Area. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5856.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
A definitive diagnosis of ocular tuberculosis (Tb) may be enhanced by quantitative real-time polymerase chain reaction (qPCR). We aimed to investigate the novel use of qPCR for detection and quantification of Mycobacterium tuberculosis genome in ocular samples of patients with suspected ocular Tb in the United States
Patients were tested on a research basis in 2008 and 2009 and had been selected upon positive tuberculin skin test (TST) and/or interferon-gamma release assay and clinical suspicion of ocular Tb. Samples from 20 eyes of 20 patients, including aqueous humor (15 samples), vitreous (3 samples), and paraffin-embedded tissue (2 samples) were analyzed. The qPCR was performed with primers targeting the IS6110 element of M. tuberculosis in addition to hydrolysis probes from the Universal Probe Library, in the Light Cycler 480 platform. Mycobacterial genome was quantified based on a standard curve with serial dilutions of mycobacterial DNA and was further correlated to clinical data.
Most patients had migrated from Tb endemic countries (90%) and 15% had history of previous exposure or treatment for Tb. TST had been positive in 85%; 15% had chest radiographs revealing lung scars consistent with Tb. Most patients had inflammatory involvement of the posterior segment of the eye, manifesting as posterior (40%), intermediate (5%), or panuveitis (25%). Four cases had positive qPCR, including two samples of aqueous humor, one of vitreous, and one of scleral biopsy tissue. Mycobacterial load in these specimens was low, from 4 to 38 genomes per qPCR reaction. Two cases with negative qPCR results were later diagnosed with retinal lymphoma by chorioretinal biopsy; two were diagnosed with toxoplasmic retinochoroiditis; and the remaining were regarded as idiopathic.
qPCR may help in the diagnosis of ocular Tb in nonendemic areas. qPCR revealed low levels of mycobacterial DNA in ocular fluids/tissue. Such low levels could be due to sequestration of the organisms in the inflamed uveal tissue and lack of free access to the aqueous humor or vitreous.
This PDF is available to Subscribers Only