Clinical and Laboratory Standards Institute guideline NBS09—Newborn Screening for X-Linked Adrenoleukodystrophy describes the currently available laboratory tests used to measure C26:0-lysophosphatidylcholine in dried blood spot (DBS) specimens. X-linked adrenoleukodystrophy (ALD) is a peroxisomal disorder not evident at birth. ALD is caused by a variant in ABCD1 resulting in defective ALD protein and impairment of peroxisomal oxidation of very long–chain fatty acids. Early detection is critical, because untreated male children with ALD have a 50% chance of developing adrenal insufficiency before the age of 10 and a 30% to 35% chance of developing cerebral disease, which has occurred as early as 2.75 years of age. This guideline includes a laboratory operations overview, with details about physical layout, instrumentation, protocols, automated methodologies, and potential for future expansion. Steps for implementing ALD newborn DBS screening, including validating the laboratory test, conducting pilot studies, and transitioning to routine screening, are discussed.

This guideline discusses the detection of X-linked adrenoleukodystrophy (ALD) by population-based newborn dried blood spot (DBS) screening. It focuses on high-throughput flow injection analysis–tandem mass spectrometry (FIA-MS/MS) and liquid chromatography–tandem mass spectrometry (LC-MS/MS) methods for detecting C26:0-lysophosphatidylcholine (LPC), the primary biomarker for ALD. This guideline is intended to provide information for incorporating ALD newborn DBS screening into the routine operations of existing newborn screening (NBS) programs. NBS09 includes background information on the biological and clinical features of ALD, the most common peroxisomal disorder, as well as other disorders of peroxisomal fatty acid oxidation, such as the Zellweger spectrum disorders (ZSDs), that could also be identified by ALD NBS. It describes preanalytical factors that affect ALD screening, including newborn DBS collection timing and specimen storage and stability. In addition to providing details on the different tandem mass spectrometry (MS/MS) analytical methods for C26:0-LPC, this guideline discusses screening strategies, testing algorithms, cutoff value determination, case definition, and risk assessment for NBS programs to consider when implementing X-linked ALD NBS. 

The intended users of this guideline are NBS laboratory, follow-up, and program personnel, public health program administrators, diagnostic medical laboratories and ALD treatment centers, health care providers (HCPs) (eg, primary care providers, neonatologists, pediatricians), regulatory agencies, public health policy makers, and manufacturers of instruments, reagents, and related products used for NBS testing. 

NBS09 discusses postanalytical short-term follow-up (STFU) and long-term follow-up (LTFU) procedures, including case tracking, as well as the diagnostic tests needed to confirm an ALD diagnosis and special follow-up considerations associated with screening for a disease with a long latency period. It contains limited discussion on diagnosis and follow-up of ZSDs and other disorders of peroxisomal fatty acid oxidation that may also be identified by ALD screening. This guideline does not cover: 

• DBS specimen collection for ALD NBS (see CLSI document NBS01) 
• Details of confirmatory diagnostic laboratory testing 
– Methods for measuring very long
–chain fatty acids (VLCFA) in plasma to confirm positive ALD newborn DBS screening results 
– Methods for ABCD1 variant analysis to confirm positive ALD newborn DBS screening results 
• Guidelines for diagnosis or treatment of ALD