What About Pediatric Reference Ranges?
by Donna Castellone, MS, MT(ASCP)S • August 03, 2023
Introduction:
Last month we looked at the issues with implementation of geriatric reference ranges for coagulation testing. This may become practice due to the expanding population of the elderly. On the flip side of the coin, the next issue would be pediatric ranges. This is an endless conundrum that so many laboratories struggle with, in particular pediatric hospitals. Many laboratories feel that this responsibility should be taken upon by the manufacturer. Well guess where the manufacturer's do their studies? Yep, in hospitals, we are right back to the circle of where do we get these samples from? How do you collect samples from healthy children, what ages? and how many samples do we need? After all of that, is there really a difference in ranges?
Process:
The FDA has committed to supporting the availability of safe and effective pediatric medical devices by providing information to support pediatric indications. These initiatives include collecting data on pediatric patients and barriers to the development of these new devices.1 The federal register has also has looked at unmet needs in this population and looked at regulatory and legal issues as well as and clinical hinderances. It encourages manufacturers to look at this issue.2
The initial issue is that pediatric patients are divided into several pediatric subpopulations:
- Neonates - from birth through the first 28 days of life
- Infants - 29 days to less than 2 years
- Children - 2 years to less than 12 years
- Adolescents - aged 12 through 21 (up to but not including the 22nd birthday)1
Weak reference ranges can make interpretation of tests difficult and can lead to inappropriate diagnosis and treatment. It is very difficult to obtain samples on healthy pediatric patients, with neonates being the hardest age group. Additionally, according to methods for obtaining RR, 120 samples are required from each age group. This is not possible for institutions to conduct. Laboratories do the best that they can to establish ranges. According to CLSI guidelines the lab can use as few as 20 samples, according to the third edition of the CLSI guideline.3 "Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory: Approved Guideline (CLSI C28-A3)."3
Additional methods include using all of the pediatric hospitalized data and removing outliers. However, this uses data from sick children and may be misleading. Coagulation RR are further complicated due to different instrument/reagent combinations. Many laboratories use published RR, however it is important to closely match the instrument, reagent as well as the testing population to your institution.
Developmental Hemostasis:
It is well known that there are significant and important differences in the physiology of coagulation and fibrinolysis in neonates and young children in the physiology of coagulation and fibrinolysis when compared with older children and adults.4 When compared with adults healthy neonates do not present with easy bruising, bleeding issues nor an increase in thrombosis for any stimulus when compared with adults. But systemic diseases may predispose neonates to increase hemorrhagic or thrombotic complications.
Developmental hemostasis reflects the issue that the hemostasis system is incompletely developed at birth and matures throughout infancy until adulthood. This includes primary hemostasis and global in vitro testing for hemostasis due to the immaturity of the neonatal hemostasis system.4
Neonates present with low levels of procoagulant factors possibly due to decreased production or accelerated clearance. The reasons are most likely unrelated to hemostasis. Low levels of vitamin K factors (II, VII, IX and X) are seen even in neonates that receive vitamin K prophylaxis at birth. AT levels are lower the first 3 months of life, lower than adults who present with AT deficiency and thrombosis. Protein C and S are low. While alpha 2 macroglobulin, an inhibitor of thrombin is twice as high in neonates as adults and may compensate for low levels of AT. Plasminogen is also low in neonates.4
Studies:
One of the first and most important study was conducted by Andrew et al on developmental hemostasis. The study showed the PT values declined in the first month of infancy and continue as they age at similar adult levels. The vitamin K dependent factors increase during the first six months of life, resulting in the decline of PT values. Prolonged aPTT may be caused by low levels of contact activation factors at birth which increase during the first six months of life. In this study fibrinogen did not statistically increase until adulthood, however there was an increase observed on the fifth day of life.5
In a study of 218 healthy children stratified by age, if was found that factors II, IX, XI and XII significantly decreased in the youngest children (< 12 months), PC and PS decreased in young childhood. The highest levels vWF was seen in youngest children, but FVIII levels were not elevated.6
A study conducted by ARUP study- n=902 in patients 7-17 yrs old (each group n=164) The PT testing was 1 second longer than adults, aPTT results were not significant. Also confirmed age dependent ranges in FVIII, IX and XI and vW testing (activity and antigen)7
A total of 320 volunteers were included in another study with the following ages: 1 month - 1 year (n = 52), 2 - 5 years (n = 50), 6 - 10 years (n = 48), 11 - 17 years (n = 38), and 18 - 65 years (n = 132). There were no statistically significant differences in the PT and aPTT within the children groups, however the PT and aPTT were significantly higher in children than adults. Fibrinogen was highest in adults and the 6-10 age group, while D-dimer levels were lower in the age group of 2-17.8
Conclusions:
When evaluating pediatric samples, it is best to use appropriate reference ranges taking into consideration ages, the analyzer and reagent. It is important to also have groups with sufficient numbers of samples to reflect the ranges. If it is not possible to conduct these ranges, the laboratory should use ranges that have been established using the same analyzer and reagents as well as subjects that represent their patient population. The source of your reference interval should be reflected in your procedures and signed off by the director. If there is no reference range for your instrument reagent combination, care should be used when interpreting coagulation results in the pediatric population.
- Pediatric Medical Devices | FDA www.fda.gov/medical-devices/products-and-medical-procedures/pediatric-medical-
- Federal Register Volume 69, Number 118 (Monday, June 21, 2004)] Pages 34374-34375] From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
- Malone, B., The Quest for Pediatric Reference Ranges, FEB.1.2012, Clinical Laboratory News
- Shoshana Revel-Vilk The conundrum of neonatal coagulopathy Hematology Am Soc Hematol Educ Program (2012) 2012 (1): 450–454. https://ashpublications.org/hematology/article/2012/1/450/83763/The-conundrum-of-neonatal- coagulopathy
- Andrew M, Paes B, Milner R, Johnston M, Mitchell L, Tollefsen DM, et al. Development of the human coagulation system in the full-term infant. Blood. 1987;70(1):165–72.
- Appel IM, et al J Thromb Haemost 2012;10:2254–63.
- Flanders M, et al Clinical Chemistry. 2005;51:1738-1742.
- Fatma Demet Arslan,1,* Muhittin Serdar,2 Elif Merve Ari,1 Mustafa Onur Oztan,1 Sureyya Hikmet Kozcu,3 Huseyin Tarhan,4 Ozgur Cakmak,4 Merve Zeytinli,1 and Hamit Yasar Ellidag5, Determination of Age-Dependent Reference Ranges for Coagulation Tests Performed Using Destiny Plus, Iran J Pediatr. 2016 Jun; 26(3): e6177.