Pediatric Lipid Disorders in Clinical Practice Workup

Updated: Jun 27, 2019
  • Author: Henry J Rohrs, III, MD; Chief Editor: Stuart Berger, MD  more...
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Workup

Approach Considerations

The 2017 American Association for Clinical Endocrinology (AACE) and American College of Endocrinology (ACE) guidelines indicate the following points should be considered when interpreting lipid profiles in children and adolescents [3] :

  • Lipid levels fluctuate during childhood and adolescence: Although plasma cholesterol levels normally peak before puberty (age 9-11 y) in boys, they often decline during puberty, along with high-density lipoprotein cholesterol (HDL-C) values.
  • Low HDL-C may not have the same implications in children as it does in adults: Over 50% of children with low HDL-C levels have normal HDL-C levels as adults. Furthermore, low HDL-C values do not constitute a hallmark of the insulin resistance syndrome in children; in this population, obesity and hypertriglyceridemia are the best predictors of this condition.
  • Lipid levels vary by sex: Throughout childhood and adolescence, plasma cholesterol levels tend to be higher in girls than in boys.

Childhood obesity guidelines

The Endocrine Society, European Society of Endocrinology, and Pediatric Endocrine Society released guidelines on the assessment, treatment, and prevention of pediatric obesity in January 2017, as summarized below. [4, 5]

Children or teens with a body mass index (BMI) ≥85th percentile should be evaluated for related conditions such as metabolic syndrome, diabetes, prediabetes, or hypertension.

Youth being evaluated for obesity do not need to have their fasting insulin values measured, because it has no diagnostic value.

Children or teens affected by obesity do not need routine laboratory evaluations for endocrine disorders that can cause obesity unless their height or growth rate is less than expected based on age and pubertal stage.

About 7% of children with extreme obesity may have rare chromosomal abnormalities or genetic mutations. Specific genetic testing is suggested when there is early-onset obesity (before age 5 years), an increased drive to consume food known as extreme hyperphagia, other clinical findings of genetic obesity syndromes, or a family history of extreme obesity.

See also other guidelines recommendation in the Guidelines section.

Next:

Laboratory Studies

See also the Guidelines section for recommendations from the American College of Cardiology, American Heart Association, and other medical societies.

Lipid testing

Lipids can be routinely measured individually as total cholesterol (TC), triglycerides (TGs), or high-density lipoprotein cholesterol (HDL-C). Using these measurements and the Friedewald equation when TG levels are less than 400 mg/dL, low-density lipoprotein cholesterol (LDL-C) can be calculated. Direct LDL measurements allow LDL-C determination on specimens when the TG level is 400 mg/dL or higher and do not require a fasting specimen. However, direct LDL-C measurements have no advantage (and add needless expense) when the TGs levels are below 400 mg/dL.

Children should be on their regular diet for 4-6 weeks before lipid testing. Recent changes in diet that may change lipid levels are an indication to delay testing. Measurements of TC and HDL-C do not need to be performed in the fasting state. However, isolated TG measurements and lipid profile measurements should follow an overnight fast of least 8 hours, preferably 12-14 hours.

Recent severe illness (eg, hospitalization within the last 4-6 wk) is a contraindication to lipid testing because significant stress can also lead to transient decreases in lipid levels or transient lipid abnormalities (eg, hypertriglyceridemia following diabetic ketoacidosis). During acute illness, lipids should not be measured unless hypertriglyceridemia is believed to be the underlying cause of the disease (eg, pancreatitis). Lipoproteins are negative acute phase reactants and their concentrations decline within 24 hours of severe acute stress. In adults, intraindividual variation in TC over the course of one year is reported to be ±8% (range 4%-11%). Intraindividual variation in TG is 13%-41%, whereas HDL-C varies by 4%-12%. Standing TC levels are 8%-12% higher than recumbent values because of a decrease in intravascular fluid that leaks into the interstitial space. The use of anticoagulants in sample tubes may lower TC levels by 3% or less.

Historically, an overnight fast was deemed necessary before lipid screening, but adult data suggest nonfasting lipids may be appropriate for initial screening for cardiovascular risk. [6, 7, 8, 9, 10] A large, cross sectional study was performed in children to assess differences in lipid values based on fasting status. [11] Mora found that although statistically significant differences existed in nonfasting lipid levels, these differences were not clinically significant, with more than 95 percent of children falling into the same classification category whether lipids were fasting or nonfasting.

Non-HDL cholesterol (ie, the TC minus the HDL-C) has been shown to be an excellent measure of risk for cardiovascular disease in adults. Both of the major non-HDL lipoproteins (LDL and very low-density lipoprotein [VLDL]) are the apoprotein-B-containing lipoproteins.

A systematic review of the evidence on benefits and harms of screening adolescents and children for heterozygous familial hypercholesterolemia (FH) indicates that screening in children can detect FH and that lipid-lowering treatment in childhood can lower lipid concentrations in the short term, with little evidence of harm. [12] However, the investigators found no evidence for the effect of childhood screening for FH on lipid concentrations or cardiovascular outcomes in adulthood, or on the long-term benefits or harms of starting lipid-lowering treatment in childhood. [12]

Guidelines

2018 American College of Cardiology (ACC)/American Heart Association (AHA), and multisocieties  [13]

  • In children and adolescents with a family history of either early cardiovascular disease (CVD) or significant hypercholesterolemia, it is reasonable to measure a fasting or nonfasting lipoprotein profile as early as age 2 years to detect familial hypercholesterolemia (FH) or rare forms of hypercholesterolemia.
  • In children and adolescents found to have moderate or severe hypercholesterolemia, it is reasonable to carry out reverse-cascade screening of family members, which includes cholesterol testing for first-, second-, and when possible, third-degree biological relatives, for detection of familial forms of hypercholesterolemia.
  • In children and adolescents with obesity or other metabolic risk factors, it is reasonable to measure a fasting lipid profile to detect lipid disorders as components of the metabolic syndrome.
  • In children and adolescents without cardiovascular risk factors or family history of early CVD, it may be reasonable to measure a fasting lipid profile or nonfasting non-HDL-C once between the ages of 9 and 11 years, and again between the ages of 17 and 21 years, to detect moderate to severe lipid abnormalities.

Normal and abnormal childhood lipid values are outlined below. [13]

TC

  • Acceptable: < 170 mg/dL (< 4.3 mmol/L)
  • Borderline: 170-199 mg/dL (4.3-5.1 mmol/L)
  • Abnormal: ≥200 mg/dL (≥5.1 mmol/L)

LDL-C

  • Acceptable: < 110 mg/dL (< 2.8 mmol/L)
  • Borderline: 110-129 mg/dL (2.8-3.3 mmol/L)
  • Abnormal: ≥130 mg/dL (≥3.4 mmol/L)

HDL-C

  • Acceptable: >45 mg/dL (>1.2 mmol/L)
  • Borderline: 40-45 mg/dL (1.0-1.2 mmol/L)
  • Abnormal: < 40 mg/dL (< 1.0 mmol/L)

TGs

  • Acceptable: (0-9 y) < 75 mg/dL (< 0.8 mmol/L); (10-19 y) < 90 mg/dL (< 1.0 mmol/L)
  • Borderline: (0-9 y) 75-99 mg/dL (0.8-1.1 mmol/L); (10-19 y) 90-129 mg/dL (1.0-1.5 mmol/L)
  • Abnormal: (0-9 y) ≥100 mg/dL (≥1.1 mmol/L); (10-19 y) ≥130 mg/dL (≥1.4 mmol/L)

Non-HDL-C

  • Acceptable: < 120 mg/dL (< 3.1 mmol/L)
  • Borderline: 120-144 mg/dL (3.1-3.7 mmol/L
  • Abnormal: ≥145 mg/dL (≥3.7 mmol/L)

American Association for Clinical Endocrinology

The American Association for Clinical Endocrinology (AACE) included optimal apoprotein-B levels in their 2012 dyslipidemia guidelines. [14]  According to the AACE, for patients at risk for coronary artery disease (CAD), including individuals with diabetes, apoprotein-B levels should be less than 90 mg/dL, whereas patients with established CAD or diabetes who have one or more additional risk factors should have an apoprotein-B level of less than 80 mg/dL. Optimal apoprotein-B levels have not yet been established for children.

The 2017 AACE and American College of Endocrinology guidelines for management of dyslipidemia and prevention of CVD included the following recommendations for children and adolescents [3] :

  • In children at risk for FH (eg, family history of premature CVD or elevated cholesterol), screening should be at age 3 years, again between ages 9 and 11 years, and again at age 18 years.
  • Screen adolescents older than 16 years every 5 years or more frequently if they have atherosclerotic cardiovascular disease (ASCVD) risk factors, have overweight or obesity, have other  elements of the insulin resistance syndrome, or have a family history of premature ASCVD.
  • An LDL-C goal < 100 mg/dL is considered “acceptable” for children and adolescents, with 100 to 129 mg/dL considered “borderline” and 130 mg/dL or greater considered “high”.

National Cholesterol Education Program

The goal of the National Cholesterol Education Program (NCEP) created in 1985 by the National Heart, Lung, and Blood Institute (NHLBI) is to educate both the public and medical professionals about the benefits of lowering cholesterol levels so as to reduce the risk for coronary heart disease. Pediatric guidelines for cholesterol screening are based on a consensus report that is updated periodically. [15, 16, 17, 18]

Abnormalities in lipid levels were initially defined as concentrations at or above the 95th percentile for TC, TGs, and LDL-C for age and sex, whereas low HDL-C concentrations were defined as lower than the 5th percentile for age and sex (see Table 3 below). Many of these cutoffs have been modified by the NCEP to define healthy or desirable levels and not merely levels outside of a certain concentration range defined statistically.

The NCEP has not defined desirable and undesirable TG levels for children and adolescents. For adults, the NCEP has defined desirable TG levels as less than 150 mg/dL, mildly elevated levels as 150-199 mg/dL, elevated levels as 200-499 mg/dL, and levels of 500 mg/dL or higher as very high.

At the University of Florida, hypertriglyceridemia in children is defined as TG levels at or above 125 mg/dL. This value of 125 mg/dL is easy to remember and approximates the mean 95th percentile for TGs in boys and girls across childhood and adolescence. Functionally mild hypertriglyceridemia in children is defined in this clinic as TG levels of 125-299 mg/dL, modest hypertriglyceridemia as TG levels of 300-499 mg/dL, marked hypertriglyceridemia as TG levels of 500-999 mg/dL, and massive hypertriglyceridemia as TG levels of 1000 mg/dL or higher. These cutoffs can be used when determining treatment approaches to hypertriglyceridemia. Desirable and undesirable fasting lipid levels in children and adults are listed in Table 3, below.

Table 3. NCEP Lipid Assessments for Children and Adults (Open Table in a new window)

Children (< 20 y)

Desirable level (mg/dL)

Borderline level (mg/dL)

Undesirable level (mg/dL)

TC

< 170

170-199

≥200

LDL-C

< 110

110-129

≥130

HDL-C*

>45

35-45

< 35

TG

< 125

...

≥125

Adults (≥20 y)

Desirable level (mg/dL)

Borderline level (mg/dL)

Undesirable level (mg/dL)

TC

< 200

200-239

≥240

LDL-C§

< 130

130-159

≥160

HDL-C||

≥40

...

< 40

TGs

< 150

150-199

≥200

* This was not established by NCEP; these values were the adult cutpoints used at the time that the pediatric NCEP guidelines were established.

This was not established by NCEP; a TG level of 125 mg/dL approximates the mean 95th percentile for TGs in boys and girls during childhood and adolescence.

In March of 2001, cutoff points for desirable and undesirable cholesterol, HDL-C, and other levels were revised in the Adult Treatment Panel III (ATPIII). [18]

§ The optimal LDL-C concentration is less than 100 mg/dL; in patients with cardiovascular disease or diabetes, the optimal LDL-C level is less than 70 mg/dL.

|| If the HDL-C level is 60 mg/dL or higher, one risk factor for coronary heart disease can be subtracted in adults.

 

National Heart, Lung, and Blood Institute

In 2011, the National Heart, Lung, and Blood Institute (NHLBI) released pediatric lipid screening and cardiovascular health recommendations. [19] These guidelines agree with most of those from the NCEP but are more specific, recommending precise ages and more aggressive repeat testing and therapy in high-risk patients. The evidence-based recommendations suggest no routine lipid screening before age 8 years.

In children aged 2-8 years who are considered to be at higher risk (eg, children with a family history of early cardiovascular disease or a parent with a TC level of 240 mg/dL or higher or known dyslipidemia; children with diabetes, hypertension, or a BMI ≥95th percentile; children who smoke cigarettes), fasting lipid profiles should be obtained on two separate occasions and the results averaged. Universal screening is recommended for low-risk individuals at age 9-11 years and again at age 17-21 years.

These recommendations for universal screening, while controversial, recognize the preponderance of evidence that high LDL-C levels are a significant contributor to heart disease, although they do not consider the lack of evidence as to whether the benefits of lifelong treatment with lipid-lowering drugs outweigh the treatment risks. [19]

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