Infectious Agents Associated Cancers Epidemiology and Molecular Biology

26

is possible for the virus to remain in a non-detectable, dormant state and then reac-

tivate years later [ 18 ].

3.5 Molecular Diagnostics

To date, highly sensitive and reproducible laboratory techniques to detect oncogenic

HPV and cervical cancer have been developed and are being used or considered in

place of cervical cytology for primary screening. The US Food and Drug

Administration has approved five of the many tests available for routine laboratory

service including [ 19 ]:

• Hybrid Capture 2 detects 13 oncogenic types of HPV (16, 18, 31, 33, 35, 39, 45,

51, 52, 56, 58, 59, and 68).

• Cervista HPV HR detects 14 HPV types (16, 18, 31, 33, 35, 39, 45, 51, 52, 56,

58, 59, 66, and 68).

• Cervista HPV16/18 detects only HPV16 and 18.


• Aptima (transcription-mediated amplification test) detects RNA from 14 HPV

types (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, and 68).

• Cobas 4800 (real-time polymerase chain reaction [PCR]-based test) detects 14

HPV types (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, and 68).

Until now, most of HPV diagnostics are mainly based on viral DNA detection for

which signal and target amplification technique are required. For example, PCR

techniques can be divided into type-specific and consensus PCRs. While the Hybrid

Capture 2 (HC2) test became the gold standard in routine HPV testing, due to its

high clinical sensitivity and its relatively high specificity. The HC2 method hybrid-

izes 13 (near) full-length stabilized synthetic RNA probes of high-risk HPV types

to denature target DNA followed by detection with antibodies and chemilumines-

cence [ 20 ].

To avoid costly validation studies for new HPV tests, internationally accepted

standards for evaluation have been defined. Meanwhile, several new HPV detection

assays have been commercialized. Three tests have received Food and Drug

Administration approval (Cervista™, signal amplification; Cobas™ HPV test, real-

time PCR; APTIMA™ HPV RNA test). Cervista can detect 14 high-risk HPV types

and is based on signal amplification technique using two simultaneous isothermal

reactions [ 20 ]. This offers an advantage over hybrid capture because it determines

the presence of sufficient DNA for reliable results [ 21 ]. Cobas™ HPV test uses

DNA technology or hybrid capture to increase the DNA signal to detectable levels.

Unlike other Food and Drug Administration (FDA)-approved DNA-based test,

APTIMA™ detects mRNA overexpressed from E6 and E7 viral oncogenes that are

entangled to carcinogenesis [ 22 ]. Among them, the Cobas HPV test has been most

broadly validated for use in triage and as an adjunct to cytology.

HPV RNA testing is another promising option with potentially higher specificity.

The HPV test is already in use for primary screening in several countries, although

Y. Li and C. Xu