Available diagnostics for disorders

Gestational diabetes

All pregnant women who do not have a prior diabetes diagnosis should be tested for gestational diabetes. If you are pregnant, you will take a glucose challenge test between 24 and 28 weeks of pregnancy.1

What tests are used to diagnose diabetes and prediabetes?

Health care professionals most often use the fasting plasma glucose (FPG) test or the A1C test to diagnose diabetes. In some cases, they may use a random plasma glucose (RPG) test.

Fasting plasma glucose (FPG) test

The FPG blood test measures your blood glucose level at a single point in time. For the most reliable results, it is best to have this test in the morning, after you fast for at least 8 hours. Fasting means having nothing to eat or drink except sips of water..

What tests are used to diagnose gestational diabetes?

Pregnant women may have the glucose challenge test, the oral glucose tolerance test, or both. These tests show how well your body handles glucose.

Glucose challenge test

If you are pregnant and a health care professional is checking you for gestational diabetes, you may first receive the glucose challenge test. Another name for this test is the glucose screening test. In this test, a health care professional will draw your blood 1 hour after you drink a sweet liquid containing glucose. You do not need to fast for this test. If your blood glucose is too high—135 to 140 or more—you may need to return for an oral glucose tolerance test while fasting.

Alzheimer’s diagnosis [https://www.alzdiscovery.org/alzheimers-disease/diagnosis-treatment]

Diagnosis

Alzheimer’s disease and related dementias are diseases of the brain, but unlike diseases that affect other organs, it’s difficult to measure changes in the brain without expensive or invasive tests. The development of the Amyvid PET scan in 2012, seed-funded by the ADDF, was an important breakthrough; it has enabled researchers to ensure that patients in Alzheimer’s trials actually have the disease. However, more reliable, affordable, and accessible diagnostics will allow us to better understand how the disease progresses, more easily identify people for clinical trials, and more accurately monitor their response to treatments.

Below are the existing types of tests.

Cognitive Tests

Your doctor may conduct a short cognitive test if you have risk factors or are showing signs of Alzheimer’s or another form of dementia. These tests can be as short as 10 minutes and include a series of questions, memorization exercises, and simple tasks, such as clock drawing. These tests alone cannot definitively diagnose the disease.

Neuroimaging

PET scans, such as Amyvid, image plaques in the brain and can detect them decades before Alzheimer’s symptoms appear. These tests are expensive and not currently covered by Medicare. Other PET scans are being developed to image other biological changes in the brain associated with Alzheimer’s. MRIs are used to detect changes in brain volume that can happen in Alzheimer’s, though these are not commonly used for diagnosis by a doctor.

Fluid-Based Tests

Levels of certain proteins, such as amyloid and tau, are detectable in cerebral spinal fluid (CSF). Researchers use CSF tests in clinical trials and other studies, but doctors rarely do so for diagnosis because the tests are invasive. Blood tests for Alzheimer’s disease are not yet available, though many are in development.

Genetic Tests [https://www.alzheimers.org.uk/about-us/policy-and-influencing/what-we-think/genetic-testing]

In the vast majority of people, any genetic risk of Alzheimer’s disease – increased or decreased – is linked not to rare mutations but to variations in a large number of susceptibility genes that they have inherited. The most common risk gene is called APOE. This gene has a number of variants, and a variant called e4 has been shown to increase risk of developing Alzheimer’s disease. However, risk genes such as APOE have a more subtle influence on someone’s chances of developing Alzheimer’s disease than the genes that are used in tests for the inherited forms of dementia.

Predictive testing for APOE variants outside of approved research studies is currently available in the UK only on a commercial basis: for a fee, companies not based in the UK will analyse a saliva sample sent off in the post. However, the results of APOE testing have low predictive value. Someone who has two copies of the higher risk APOE variant e4 is not certain to develop Alzheimer’s disease, while someone who has other variants still might. This poor predictive value is why APOE testing is not recommended (outside research studies) or available within the NHS.

Pulmonary Function Tests [https://stanfordhealthcare.org/medical-conditions/chest-lungs-and-airways/interstitial-lung-disease/diagnosis.html]

Diagnostic tests that help to measure the lungs’ ability to exchange oxygen and carbon dioxide appropriately. The tests are usually performed with special machines into which the person must breathe.

Spirometry -A spirometer is a device used by your physician to assess lung function. The evaluation of lung function with a spirometer is one of the simplest, most common pulmonary function tests and may be necessary for any/all of the following reasons:

  • To determine how well the lungs receive, hold, and utilize air
  • To monitor a lung disease
  • To monitor the effectiveness of treatment
  • To determine the severity of a lung disease
  • To determine whether the lung disease is restrictive (decreased airflow) or obstructive (disruption of airflow)

Bronchoscopy

Bronchoscopy isthe examination of the bronchi (the main airways of the lungs) using a flexible tube (bronchoscope). Bronchoscopy is performed under anesthesia and helps to evaluate and diagnose lung problems, assess blockages, obtain samples of tissue and/or fluid, and/or to help remove a foreign body. Bronchoscopy may include a biopsy or bronchoalveolar lavage.

Lung Biopsy

To remove tissue from the lung for examination in the pathology laboratory. VATS, video assisted thoracoscopic surgery, is the most common way to get lung tissue for biopsy for this group of diseases. It is done in the operating room using scopes through the chest wall to obtain tissue.

Genetic Testing for Non-Communicable diseases

Genetic testing has not yet been made a part of an average clinic’s repertoire of diagnostic tests. Genetic tests, especially for these non-communicable diseases are mostly offered by 3rd party genetics laboratories and companies such as PHIX Genomics. These tests aren’t the first choice for many healthcare professionals when diagnosing non-communicable diseases, and are often offered only if the patient wants them. However, slowly we are realizing the increasing correlation and causation between these diseases and its genomic roots. We are yet to reach that point, and as of now most of the information regarding genetic variants of non-communicable diseases mostly point to a higher susceptibility of developing the disease rather than finding actual pathogenic genes, which is why genetic tests are yet to become a priority when diagnosing these types of diseases.

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