Development and Evaluation of Loop-Mediated Isothermal Amplification Assay for Rapid and Inexpensive Detection of Cytomegalovirus DNA in Vitreous Specimens from Suspected Cases of Viral Retinitis

A loop-mediated isothermal amplification (LAMP) assay for the rapid detection of cytomegalovirus (CMV) was developed and evaluated. The LAMP assay specifically amplified only CMV DNA, and no cross-reactivity with the DNA of herpes simplex virus type 1, varicella-zoster virus, adenovirus, Aspergillus flavus, or Staphy-lococcus aureus was observed. The sequences of the LAMP assay-positive CMV products were perfectly (100%) matched with the CMV sequence deposited in the GenBank database. The sensitivity of the LAMP assay was found to be 10 copies/l of CMV DNA. Vitreous samples from 40 patients with suspected retinitis were subjected to LAMP and real-time PCR for the detection of CMV. Of 40 patients with suspected viral retinitis, 10 tested positive for CMV by the real-time PCR and LAMP assays. A 100 % concordance was observed between the results of the two methods. The LAMP assay is a rapid, highly specific, and sensitive method for the diagnosis of retinitis caused by CMV. Viral retinitis is commonly caused by herpes simplex virus type 1 (HSV-1), HSV-2, varicella-zoster virus (VZV), cyto-megalovirus (CMV), and occasionally, Epstein-Barr virus (EBV) (7). In patients with atypical features and in the early stages of ocular manifestations, clinical differentiation betwee