Click here for more information about laboratory operations and procedures
|Utilization Guidelines||This should only be ordered in patients who have rising plasma CMV viral loads after at least 3-4 weeks or more of anti-viral therapy. CMV viral loads commonly rise during the first 2-3 weeks of therapy but this does not indicate resistance unless the patient has had recent exposure to the specific drug.|
|Method||PCR, DNA sequencing|
|Container type||Lavender top|
|Amount to Collect||4 mL blood|
|Sample type||EDTA plasma|
|Preferred volume||2 mL plasma|
|Min. Volume||1.5 mL plasma|
|Processing notes||Separate plasma within 2 hours of collection and transfer to sterile screw-top plastic vial.
Freeze plasma at -20C and ship to China Basin and ViraCor on dry ice.
Order ViraCor test # 5600
Call ViraCor for authorization on anything other than plasma. Sequencing assays are very sensitive to inhibition, and processing of other sample types, including CSF and BAL, may be affected by PCR inhibitors that affect the result.
|Ref Lab Rejection Criteria||CMV DNA concentrations too low to allow antiviral resistance testing (<1000 copies/mL for plasma)|
|Synonyms||CMV; CMV susceptability; CID; CMV resistance; CMV inclusion disease|
|Stability||Room temperature 4 days, refrigerated 1 week, frozen at -20C 1 month|
|Turn around times||Set up Monday - Friday. Turnaround 4-6 days|
|Additional information||Resistance of CMV to antivirals usually requires weeks to months of drug exposure and should not be ordered in the first few weeks of treatment, even if viral copy numbers appear to be rising.
Assaying CMV susceptibility to one or more antivirals phenotypically, by culture, can take several weeks and requires a viable viral isolate. Genotypic testing, i..e.,determining whether the virus has one or more mutations associated with resistance, can be performed in a few days and directly on clinical specimens if sufficient viral copy numbers are present. Two genes, UL97 and UL54, the DNA polymerase, are sequenced to permit determination of resistance to ganciclovir, cidofovir and/or foscarnet.
If a mutation has been detected in either the UL97 or UL54 Gene Targets, the mutation site is indicated. A result of "None Detected" indicates that no mutations were detected for that gene target.
UL97 mutations analyzed that have been confirmed by marker transfer experiments include M460V, M460I, H520Q, 590-593DEL, 591-594DEL, 591-607DEL, A594V, A594T, A594P, 595-603DEL, L595F, L595S, D595DEL, E596G, G598S, K599T, 600DEL, 601DEL, C603W, C607F, C607Y. Other mutations analyzed that habe been found in resistant clinical isolates include C592G, 594-601DEL, and L595W.
UL54 mutations analyzed that have transferred antiviral resistance to recombinant viruses include D301N, N410K, F412C, F412S, L501I, K513N, L516R, D588N, T700A, V715M, E756D, E756K, E756Q, V787I, V787L, L802M, and A809V. Other mutations not confirmed by transfer experiments, but associated with antiviral resistance include N408D, F412V, D413E, L501F, T503I, K513R, K513E, P522A, P522S, L545S, D588E, G678S, Y751H, V781I, K805Q V812L, T821I, T838A, G841A, 981-2DEL, and A987G.
|CPT coding||83891 (x15) 83898 (x5) 83904 (x10) 83912 (x1) 83890 (x1) 83909 (x10)|
|Last Updated||1/3/2013 12:34:49 PM|
If you have additional questions regarding this test, please call: 415-353-1667