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HPV is
the name given to a group of viruses that includes more than 100
known types. There are over 50 viral types that are known to infect
the genital tract. Presently, HPV infection is the most known
sexually transmitted disease worldwide estimated to be present in at
least 50% of sexually active males and females. HPVs selectively
infect the skin and mucous membrane's epithelium. The infection may
be asymptomatic, produce warts or is even associated with a variety
of benign and malignant neoplasms.
Why is HPV testing important?
Most
infected persons are unaware that they are indeed infected, yet they
can still transmit the virus to their sexual partner.
Low risk
HPVs are those types (6, 11, 42, 43, 44) that may cause changes on
PAP smear but do not progress to cancerous changes.
High risk
HPVs (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 68) may also
cause changes to PAP smear but rarely progress to cancer.
Thus HPV
status and information about viral type(s) involved in the infection
have important clinical significance.
HPV DNA Testing
It is
adviced that any abnormal or borderline smear test results should
be tested for HPV DNA. The presence of koilocytes in the smear test
is indicative of an HPV infection. HPV DNA testing together with PAP
smear is a very useful tool for the prevention of cervical cancer.
Test Methodology
MLS BioDNA Ltd is offering HPV DNA testing by PCR. DNA is
extracted from a cervical brushing and amplified by PCR using a set
of primers that detects a very wide range of HPV types. When
compared to other sets of primers, it was shown that these primers
are more sensitive in detecting a wider range of viral types [1]. If
a test is positive, identification of the viral type is done by
direct DNA sequencing.
Sample Requirements
A
cervical brushing sent to the laboratory either dry or
suspended in sterile normal saline, at ambient temperature.
The
sample should preferably be left unfixed.
A
cervicovaginal lavage is also good for testing.
A
properly filled sample submission form should be sent together with
the sample. Sample submission forms can be downloaded from
here.
Samples
should be sent to the laboratory as quickly as possible after being
taken and should never be exposed to extremes of temperature.
Cervical
brushes can be obtained from the laboratory free of charge.
Preparation for sampling
Before
taking the sample for HPV DNA testing it is important to ask the
patient:
All the
above mentioned factors might result in a false negative result due
to problems with DNA extraction or PCR inhibition.
Results
The test
result is issued within 10 days after receipt of sample.
A
positive test result indicates HPV infection but does not mean that
the person is going to develop cancer. Further testing (biopsy or
colposcopy) can be suggested by the physician especially if cellular
changes were reported by cytology.
A
negative result does not exclude completely the possibility of a HPV
infection. False negative results can result due to very low levels
of infection, sampling errors or due to the presence of a
different HPV type other than those that are detected by the system.
Testing should be repeated for those individuals having cellular
changes but a negative HPV test.
It was
shown that a significant number of patients diagnosed with
koilocytosis and CINI did not in fact have HPV infection [2].
Besides this low grade lesions can regress spontaneously. Also
koilocytosis was reported in CMV infection in the absence of an HPV
infection, showing that similar cellular changes can be caused by
other viral infections [3].
If you would like more information please
call the laboratory on 2398 0148.
References
[1]
Fuessel Haws AL, He Q, Rady PL et al. Nested PCR with the PGMY09/11
and GP5(+)/6(+) primer sets improves detection of HPV DNA in
cervical samples. (2004) Journal of Virological Methods
122: 87 - 93.
[2] Abadi
MA, Ho GYF, Burk RD et al. Stringent criteria for histological
diagnosis of koilocytosis fail to eliminate over diagnosis of human
papilloma infection and cervical intraepithelial neoplasia grade 1.
(1998) Human Pathology 29: 54 - 59.
[3]
Daxnerova Z, Berkenova Z, Kaufman R & Ervin A. Detection of human
cytomegalovirus DNA in 986 women studied for human Papillomavirus
associated cervical neoplasia. (2003) Journal of Lower Genital
Tract Disease 7: 187 - 193.
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