16.  Diagnostic laboratory procedures

Q. 2. What are the indications of following investigations in dentistry:

(a) biopsy, (b) sialography and (c) exfoliative cytology?

Ans.

Biopsy

Biopsy is the removal of tissue from living individual for microscopic examination and precise diagnosis of the lesion.

Various types of biopsy are as follows:

i. Excisional biopsy

ii. Incisional biopsy

iii. Aspiration biopsy

iv. Punch biopsy

v. Frozen section biopsy, etc.

Biopsy in diagnosis of malignant lesions is an absolute requirement before ablative cancer therapy can be initiated.

The biopsy specimen obtained should be representative of the lesion under investigation. Adequate depth, that is through the epithelium into connective tissue is necessary to determine the integrity of the basement membrane and to search for nests of invasive tumour cells.

Most pathologists request that the specimen include a zone of adjacent, clinically normal tissue in order to recognize malignant changes; however, when ulceration is present, specimens obtained from the ulcerated areas may reveal only nondiagnostic necrosis.

Inclusion of some clinically uninvolved tissue in the specimen when ulceration is present, usually ensures a representative sample of active nonnecrotic tumour.

Intentional excisional biopsy, that is total removal of all abnormal tissue for diagnostic purposes has absolutely no role in the diagnosis of oral cancer.

Planned excisional biopsy of a lesion clinically suspected to be malignant cannot be justified by any rationale and should be condemned.

Adequate excision of a malignant lesion usually requires at least a 1.5 cm margin of clinically uninvolved tissue along each periphery; if the diagnosis is benign, it is impossible to justify removal of such a large block of tissue.

If the diagnosis is malignant, any specimen with less than 1.5 cm of clinically normal tissue along each margin is inadequate, and retreatment of the lesion would be mandated.

Excision of a lesion for diagnosis is justifiable only when the lesion is almost certainly benign or when the lesion is so minute that total removal is required, to ensure an adequate volume of tissue for microscopic evaluation.

In most cases, every reasonable attempt should be made to obtain an incisional specimen, that is removal of small representative portion of the lesion.

Sialography

Sialography is a specialized radiographic view taken by introduction of the radiopaque dye into the ductal system of the major salivary glands, mainly parotid and submandibular.

This technique is used to examine the ductal and acinar systems of the major salivary glands.

Sialography will aid in the diagnosis in cases where the radiographs are negative and will demonstrate a filling defects, narrowing of ducts at the site of the stone, and dilation of the duct proximal to the stone.

This technique is no longer considered as desirable, since there is some danger of glandular damage by the injected dye, and in patients with severe Sjogren the dye will remain in the gland interfering with future tests.

Exfoliative cytology

Intraoral exfoliative cytologic study, although eliminating many of the disadvantages of the biopsy, by no means supplants the usual biopsy study.

Over the last 25 years, considerable experience has been gained with the exfoliative cytologic techniques in oral diagnosis that were originally developed by Silverman and Sandler.

A variety of oral diseases have been studied with this technique, but the procedure is of most value in the evaluation of suspected malignancies, especially when these present as ulcerated or red nonkeratinized lesions.

Oral cytology should never be relied on for diagnosis of an oral lesion simply because it may be easier to obtain than a biopsy.

Once a lesion is suspected to have a slightest chance of being malignant, the lesion should be biopsied adequately at the earliest opportunity.

With these considerations in mind, Papanicolaou-stained smears of oral mucosal lesions are indicated in the following circumstances in clinical dentistry:

i. For rapid laboratory evaluation of an oral lesion that on clinical grounds is thought to be malignant. For example, in the case of advanced malignancies where delay or preliminary incision of the lesion is not warranted, laboratory confirmation of the clinical impression often can be obtained by a Papanicolaou-stained smear in 1–2 days.

ii. For laboratory evaluation of an oral lesion that on clinical grounds is thought to be premalignant and for which the dentist is unable to obtain permission for a biopsy.

iii. In patients with multiple premalignant lesions, biopsy of multiple lesions or entire removal of extensive lesions may not be feasible, and cytology may be a very practical adjunct to biopsy.

iv. For sequential laboratory evaluation of an area of mucosa that has previously been treated by excision or radiation to remove a malignancy. Successive biopsies are often not possible, and cytology provides something better than simple clinical observation, especially where previous treatment has led to scarring or other tissue change.

v. For evaluation of vesicular lesions (herpes simplex, pemphigus, pemphigoid) where facilities for rapid evaluation of a Tzanck smear are not available or where more detailed cytology is required.

Procedure

The clinical value of exfoliative cytology is directly related to the skill of the cytologist and his experience with oral smears.

A dentist who proposes to use this laboratory procedure should first determine, which laboratories are available to him to routinely handle oral smears.

The laboratory will frequently provide a kit (slides, cytoscraper, mailing tube) with instructions for obtaining, fixing, and transporting the specimen.

In general, the preparation of the smear is similar to that used to obtain oral smears for other purposes with the exception that firm pressure with a wooden or steel scraper must be used to ensure that adequate numbers of cells are obtained, and the smear must be fixed immediately. For this purpose, an aerosol fixative such as Spraycyte or 95% alcohol may be used.

Oral exfoliative cytology has been used for the study of other nonmalignant changes in the oral cavity, for example, studies of buccal mucosa in various anaemias and of the maturation of the buccal mucosa with the menstrual cycle.

Oral cytology is generally most helpful in evaluation of nonkeratinized ‘red patches’ or ulcerative lesions of the oral mucosa. Specimens obtained from heavily keratinized ‘white patches’ are composed mainly of superficial squames, and the more immature basal cells are not represented on the smear.

The standard classification used in oral cytology reports is as follows:

Class I, normal cells.

Class II, some atypical cells, but no evidence of malignancy.

Class III, changes in nuclear pattern of indeterminate nature; no definite evidence of malignancy, but clearly aberrant cells are present.

Class IV, suggestive of malignancy.

Class V, obvious malignant changes.

A report of class III, IV, or V changes should always be followed by a biopsy of the lesion.


Q. 3. ESR.

Ans.

The erythrocyte sedimentation rate (ESR) measures the rate at which RBCs sediment in a tube of plasma.

The rate is accelerated when changes in plasma proteins cause the RBCs to aggregate or when there are changes in the physicochemical properties of plasma or the red cell surface.

The test is helpful in following the progress of some chronic infections (tuberculosis and osteomyelitis) as well as diseases characterized by altered globulins such as the collagen diseases, nephritis, rheumatic fever, and the dysproteinemias.

It is claimed to be more sensitive than temperature, WBC count, weight and subjective symptoms as an indication of progress of some diseases.

Marked elevations usually indicate the presence of disease, the exact nature of which should be investigated.

In the Westergren method, a graduated sedimentation tube is filled with oxalated blood and placed in an absolutely vertical position.

The erythrocyte level is read at 10 minute intervals and at the end of the hour.

The generally accepted normal sedimentation rates in 60 min for this method are males, 015 mm; females, 020 mm.

The sedimentation rate may be increased in women with intrauterine contraceptive devices (IUDs) and women taking an ovulatory steroids (oral contraceptives).

This test is also of considerable importance in the diagnosis of giant cell arteritis (temporal arteritis) and a closely related disease, polymyalgia rheumatica, which are uncommon but clearly defined causes of recurrent facial pain.

Short notes

Q. 1. Brush biopsy.

Ans.

i. Brush biopsy technique is only a screening tool, which enables a transepithelial capture of cells.

ii. In this technique, a brush is rotated against the tissue until slight bleeding is observed, indicating that the brush has reached the basement membrane.

iii. The cellular aggregate on the brush is transferred to a glass slide, fixed and then analysed by computer scans and pathologists trained specifically in oral brush biopsy interpretation.

iv. The technique can be applied to a wider segment of the population.


Q. 2. Schirmer test.

Ans.

i. Schirmer test is one of the tests to evaluate lacrimal gland function in suspected Sjogren patients.

ii. The Schirmer test consists of placing a strip of filter paper in the, lower conjunctival sac.

iii. Normal patients will wet 15 mm of filter paper in 5 min. Patients with Sjogren syndrome will wet less than 5 mm of filter paper.


Q. 3. Paul-Bunnell test.

Ans.

Patients with infectious mononucleosis develop an increased serum titre of an antibody that cross-reacts with red blood cells from other species (heterophil or Forssman antibody).

Whenever a patient is suspected of having infectious mononucleosis because of symptoms, examination findings, or haematologic abnormalities, ‘the titre of heterophil antibody’ is used to confirm the diagnosis.

The traditional test for heterophil antibody is based on agglutination of sheep red cells and is known as the Paul-Bunnell test.

The (Davidsohn) differential test is a modification of the Paul-Bunnell test, in which the serum titre of sheep agglutinins is measured before and after absorption of the patient’s serum with beef or guinea pig red cells to make the test more specific for detecting infectious mononucleosis.


Q. 4. Oral exfoliative cytology.

Ans.

Intraoral exfoliative cytology, originally developed by Silverman and Sandler, although eliminates many of the disadvantages of the biopsy, by no means supplants the usual biopsy study.

A variety of oral diseases have been studied with this technique, but the procedure is of most value in the evaluation of suspected malignancies, especially when these present as ulcerated or red nonkeratinized lesions.

The clinical value of exfoliative cytology is directly related to the skill of the cytologist and his experience with oral smears.

The laboratory will frequently provide a kit (slides, cytoscraper, mailing tube) with instructions for obtaining, fixing and transporting the specimen.

Oral cytology is generally most helpful in evaluation of nonkeratinized ‘red patches’ or ulcerative lesions of the oral mucosa.

Only gold members can continue reading. Log In or Register to continue

Apr 11, 2016 | Posted by in Orthodontics | Comments Off on 16.  Diagnostic laboratory procedures
Premium Wordpress Themes by UFO Themes