What are Screening Tests?
It is important to gain an understanding of how HHT impacts the internal organs. There are several tests that everyone who is known or suspected to have HHT should have done. These are called screening tests since the abnormality is looked for prior to its causing a problem. Lung and brain AVMs are the only problems associated with HHT for which we recommend pre-symptomatic, preventive screening.
A screening test will:
- Determine whether you meet the criteria for a diagnosis of HHT
- Look for pulmonary (lung) AVMs and cerebral (brain) AVMs since these can cause serious life-threatening events without warning
Pulmonary AVMs (Lung AVMs)
Screening for lung AVMs (PAVM) is dependent on the age of the individual, and to a lesser degree, their symptoms. Preferably, individuals with HHT will have had screening for PAVMs by the time of their early teens. If a pregnant woman has not had a recent evaluation for PAVM, it is imperative for her to do so as soon as pregnancy is recognized. In many cases, an HHT Treatment Center will be able to use tests performed by another facility unless the original tests are too old, the old test is not of high enough quality, or the old test was performed a little differently. PAVMs larger than a certain size should be embolized to prevent complications like brain abscesses and strokes. For smaller PAVMs, antibiotics prior to most dental work and certain other non-sterile invasive procedures, like colonoscopy, are recommended. Until PAVMs are excluded by testing, a person over the age of 10 with known or suspected HHT should take antibiotics before all dental cleanings, work and other medical procedures which have a risk of introducing bacteria into the bloodstream.
The recommended test of choice for PAVM screening in adults and also used in older children and adolescents. This test uses sound waves (ultrasound) to determine if injected saline bubbles can get through the lung circulation and be seen back in the heart, on the left side. This is called a shunt. It is a very sensitive test but not everyone with a “positive” or “abnormal” bubble echo test has a Pulmonary AVM large enough to re- quire treatment by embolization. To determine if treatment is necessary, a chest CT scan should be done if the bubble echo is more than minimally abnormal.
A standard X-ray of the lungs will let doctors look at the size of your heart and the condition of your lungs.
During this test you breathe pure oxygen for 15 minutes with a nose clip on, then a small sample of arterial blood is collected from an artery in your wrist. This is not a routine screening test, but rather is used to assess a patient before and after treatment for PAVMs.
This is like a 3-dimensional high-resolution X-ray of your lungs. If “X-ray dye” is used, an IV will need to be started.
A catheter is inserted through a large vein in either your leg or neck, and is passed up into the arteries of the lungs. This involves one or more injections of “X-ray dye” into the arteries to expose the AVM.
Annual Visit with your Primary Care Physician (PCP)
A yearly evaluation by your PCP is recommended, along with an annual check of ferritin levels, hematocrit, and hemoglobin. Without periodic check- ups with an HHT expert, HHT related medical problems are often missed, misdiagnosed or mismanaged which can lead to catastrophic events. Most HHT Centers of Excellence will see patients every 3-5 years, or as symptoms warrant.
Children Need Screening Too - Published in Pediatric Nursing (2011) and written by Lynne Sekarski, MSN, RN, CPN and Lori Spangenberg, BSN, RN (HHT Center, St. Louis Children's Hospital, Washington University).
Not all children show signs of HHT (i.e., nosebleeds and “red spots” on the skin). Children without nosebleeds or other symptoms of HHT can have AVMs in their lungs or brain that require intervention.³ In fact, potentially life-threatening manifestations of HHT have been identified in asymptomatic children under 12 years of age.¹
- If a family has had genetic testing, then all children in the family should be tested against the identified gene mutation.
- If the family gene has not been identified, then a clinical evaluation will be required.
All children diagnosed with HHT should receive a pediatric screening for HHT. A screening appointment consists of a thorough history, a physical examination, screening for lung AVM (see section below), and brain magnetic resonance imaging (MRI) with and without contrast.¹ If a child’s initial screening is not conducted at an HHT Center, it would be recommended that all patients with a positive MRI or an abnormal echobubble test consult an HHT Treatment Center for consideration of more invasive testing and further treatment.
According to the Clinical Guidelines², there is not consensus on the recurring tests of children with HHT. However, it is recommended by most HHT Centers that:
- Children with possible or confirmed HHT should be screened for Brain AVM in the first year of life (or at the time of diagnosis) and at least one follow-up MRI at puberty since brain AVM development appears to correlate with times of growth.
- Lung AVM screening is recommended every 3-5 years, if a pulse oximetry test result is 97% or higher. If a pulse oximetry result is lower than 97%, or a child is short of breath, additional tests or treatment may be required.
Should Your Child be Screened for Lung AVMs?
Since the 1980’s we have learned a great deal about pulmonary (lung) arteriovenous malformations (PAVMs) in adults. We know that they frequently cause neurological complications, such as stroke or brain abscess. Multiple studies have shown that treatment of PAVMs is safe and effective. For this reason we recommend screening for PAVMs in all adults.
However, it is less clear what constitutes optimal screening and treatment of PAVMs in children. The largest study of PAVM in children reported on 42 children who underwent embolization of PAVM from 3 HHT Centers of Excellence. Neurological complications such as stroke were less common in children compared with adults. The children that did have neurological complications tended to have low oxygen levels in the blood or felt short of breath when exercising. Embolization techniques were simlar to those used for adults except that general anesthesia or heavy sedation were more commonly required for children. Embolization was effective and well tolerated by children and about 15% required repeat embolization at some time in the future. In some children the repeat embolizations were required because blood flow returned through an embolized PAVM – so called re-perfusion. Although it is not clear-cut, some experts believe that children have more re-perfusion after embolization than adults. This may be due to the fact that they are growing and thus their blood vessels are growing too. This means that children need to be followed closely after embolization to make sure that their PAVMs remain closed.
Based on the fact that some children did have complications from PAVM s, HHT medical professionals currently advocate screening for PAVM in all children of a parent who has HHT. Bubble echo is the recommended screening test for symptomatic children who have low oxygen levels, complain of shortness of breath, have a hard time keeping up in sports, or have had prior neurologic complications. However, the best screening test for asymptomatic children is controversial: some HHT Treatment Centers perform pulse oximetry before the age of 10 followed by bubble echo after the age of 10-14; other HHT Treatment Centers perform bubble echo at all ages. The optimal management of children who are diagnosed with PAVM is complicated and should be done in consultation with HHT Center of Excellence.
- Sekarski, L., Spangenberg, L. (2011). Hereditary Hemorrhagic Telangiectasia: Children Need Screening Too. Pediatric Nursing, Vol. 37, No. 4, 163-168.
- Faughnan, M. et al. (2009). International Guidelines for the diagnosis and management of Hereditary Hemorrhagic Telangiectasia. Journal of Medical Genetics, 48(2), 73-87. Advance online publication. Doi:10.1136/jmg.2009.069013.
- Mei-Zahav, M. et al. (2006). Symptomatic children with Hereditary Hemorrhagic Telangiectasia. Archives of Pediatric Adolescent Medicine, 160, 596-601.
- Olitsky, S. (2010). Hereditary Hemorrhagic Telangi- ectasia: Diagnosis and Management. American Family Physician, Vol. 82, No. 7, 785-790.