Sexual Health: The Currently Available Methods For HPV Testing In Women

What is HPV?

Human Papillomavirus is the most common type of Viral Sexually Transmitted Infection. Although the clearance rate for HPV is high, it has the deadly potential of progressing to cervical carcinoma. Certain HPV strains result in simple warts on the skin surface while high-risk HPV strains affect the mucosal surfaces such as the cervix.

Diagnostic Methods For HPV

HPV Testing

The diagnosis of human papillomavirus (HPV) infection can be deduced from morphological, serological, and clinical findings. With the advancement in medical science, there are many different methods currently available for testing for HPV. However, each method is different in terms of sensitivity, specificity, and convenience. Let us look in detail into each of the available diagnostic methods for HPV.

1. Based on cell morphology

a. Pap smear/tissues:

This process involves taking a smear sample from the cervix to examine the presence of HPV by analyzing the cell morphology of the sample obtained.
Sensitivity: Low
Specificity for Cervical Cancer: High

b. Colposcopy:

Colposcopy is the direct visual examination of the cervix using a special instrument called a Colposcope. It is useful to examine dysplastic changes that can be directly visualized.
Sensitivity: Moderate
Specificity for Cervical Cancer: Low

c. Visual inspection:

This procedure is simply examining the vagina and cervical walls with the naked eye. Although the easiest method, it has limited efficacy.
Sensitivity: Low
Specificity for Cervical Cancer: Low

2. Detection of HPV proteins

Immunological detection of HPV has limited use. The limitation to detecting HPV in human cells or tissues is mainly due to its inability to detect proteins in the early stages as the proteins are only detectable in productive infections, and even in productive infections, the amount of protein produced in the early stages is too low to be detectable. Therefore, although many methods exist to detect HPV proteins, it is not useful in the early clinical diagnosis of HPV. These methods are also technically cumbersome and time-consuming.

a. Immunocito/ histochemistry

Sensitivity: Low
Specificity for Cervical Cancer: Low

b. Electron microscopy

Sensitivity: Low
Specificity for Cervical Cancer: Low

c. Western blots

Sensitivity: Low
Specificity for Cervical Cancer: Moderate

3. Detection of HPV genomes

Accurate diagnosis and identification of HPV are dependent on molecular biology. The DNA of HPV is double-stranded with 8000 base pairs and a distinct gene organization. Hence, HPV DNA identification is the current choice of test for HPV.

a. Direct methods:

Although excellent to detect HPV DNA, it is time-consuming and requires a sample rich in HPV nucleic acids. Direct detection of HPV DNA can be done by hybridization procedures such as:

• Southern blot

Sensitivity: Moderate
Specificity for Cervical Cancer: High

• ISH

Sensitivity: Moderate
Specificity for Cervical Cancer: Moderate

• Dot blot

Sensitivity: Low
Specificity for Cervical Cancer: High

b. Signal amplification:

Hybrid Capture:

Hybrid Capture is currently one of the most widely used gene detection technologies.

Sensitivity: High
Specificity for Cervical Cancer: High

c. Target amplification:

In this method, the viral genomes are selectively amplified by a series of polymerization steps, which result in an exponential and reproducible increase in the HPV nucleotide sequences present in the biological specimen. Target Amplification is done by:

PCR and Hybrid Capture

Sensitivity: Very High
Specificity for Cervical Cancer: Very High

4. Detection of anti-HPV antibodies

The antibodies against HPV are non-specific, non-sensitive, and difficult to detect. Thus, this technique is not currently used in the clinical diagnosis of HPV.