Pathology Lab Techniques to Diagnose Disease

Cellular Methods to Identify Viral Infections and Cancer

Oct 8, 2009

Pathology is a diverse, important part of medicine in the study of disease. New research in diagnostic methods allow easier, faster treatment of cancer and infections.

Pathology is derived from the Greek pathos or suffering and logos, to study. Cellular pathology or histopathology uses scientific methods to make diagnoses and to investigate the causes and effects of disease on the body. This includes examining structural changes in diseased tissues at visible to the eye (macroscopic) and microscopic levels.

The Preparation of Tissue Samples to Identify Disease

Small specimens of diseased tissues can be obtained through a hollow needle in a biopsy or by an endoscopy. The tissue samples are then processed into thin sections to view under a microscope.

To make it easier to visualize the many structures in the cells, a tissue sample usuaully requires staining. The most common stains are haematoxylin and eosin (H&E). Haemotoxylin is a basic dye that binds to structures including DNA and stains nuclei blue. Eosin stains cytoplasm and other extracellular structures, red. Other stains are used for specific structures.

Immunohistochemistry is a more sensitive and specific method for marking substances in a tissue section. It uses immune binding of a specific antibody solution to mark any corresponding antigens in the sample. This method is often used to identify bacteria, viruses and tumours.

Electron microscopy which uses shorter wavelengths to magnify images up to 10,000 to 25,000 times, can then identify the sample components.

Molecular Techniques Identify Changes in DNA

Molecular techniques in pathology are used to understand the changes in nucleic acids (DNA) that occur during the development and progression of a disease. Two common methods are the polymerase chain reaction (PCR) and in-situ hybridization.

PCR is a valuable technique used to amplify the DNA available for analysis. This is important in identifying a disease, tumour or cause of infection. In-situ hybridization identifies specific nucleic acids within tissue sections using specific ‘probes’ which bind to a specific nucelic acid. The marked probes are then seen using a fluorescent dye.

Cytopathology is the study of preparations in which cells are separated from each other. A common example are cervical cells obtained in a Pap smear. The cells are then examined to look for any cancerous or pre-cancerous changes. Other methods includes collecting cells from fluids such as urine and by fine needle aspiration cytology in which cells are extracted from suspected tumours with a needle and syringe.

Pathology is a vital part of medicine and has many diverse aspects to it. It allows doctors to make accurate diagnoses and to understand the natural progression of a disease which is important for patient prognosis (how well the patient may fare).

It also allows strategies to screen for diseases and to detect diseases such as certain cancers very early, which increases the chances of treating it.

Clinical and laboratory techniques in pathology are diverse and research to improve methods and discover new ones is ongoing.

The copyright of the article Pathology Lab Techniques to Diagnose Disease in Medical Biotechnology is owned by Noreen Kassem. Permission to republish Pathology Lab Techniques to Diagnose Disease in print or online must be granted by the author in writing.