Gaucher Disease Diagnosis Using Lyso-Gb1 on Dry Blood Spot Samples: Time to Change the Paradigm?

Abstract

For years, the gold standard for diagnosing Gaucher disease (GD) has been detecting reduced β-glucocerebrosidase (GCase) activity in peripheral blood cells combined with GBA1 mutation analysis. The use of dried blood spot (DBS) specimens offers many advantages, including easy collection, the need for a small amount of blood, and simpler transportation. However, DBS has limitations for measuring GCase activity. In this paper, we recount our cross-sectional study and publish seven years of experience using DBS samples and levels of the deacylated form of glucocerebroside, glucosylsphingosine (lyso-Gb1), for GD diagnosis. Of 444 screened subjects, 99 (22.3%) were diagnosed with GD at a median (range) age of 21 (1-78) years. Lyso-Gb levels for genetically confirmed GD patients vs. subjects negative to GD diagnosis were 252 (9-1340) ng/mL and 5.4 (1.5-16) ng/mL, respectively. Patients diagnosed with GD1 and mild GBA1 variants had lower median (range) lyso-Gb1, 194 (9-1050), compared to GD1 and severe GBA1 variants, 447 (38-1340) ng/mL, and neuronopathic GD, 325 (116-1270) ng/mL (p = 0.001). Subjects with heterozygous GBA1 variants (carrier) had higher lyso-Gb1 levels, 5.8 (2.5-15.3) ng/mL, compared to wild-type GBA1, 4.9 (1.5-16), ng/mL (p = 0.001). Lyso-Gb1 levels, median (range), were 5 (2.7-10.7) in heterozygous GBA1 carriers with Parkinson's disease (PD), similar to lyso-Gb1 levels in subjects without PD. We call for a paradigm change for the diagnosis of GD based on lyso-Gb1 measurements and confirmatory GBA1 mutation analyses in DBS. Lyso-Gb1 levels could not be used to differentiate between heterozygous GBA1 carriers and wild type.

Keywords: Gaucher disease; diagnosis; dry blood spot; glucosylsphingosine; lyso-Gb1.

Figure 1

Age at diagnosis of GD. Thirty children were diagnosed at the age of 0–10 years, 18 at the age of 11–20 years, 25 at the age of 21–30 years, nine at the age of 31–40 years, nine at the age of 41–50 years, four at the age of 51–60 years, and four at the age of over 61 years.

Figure 2

Lyso-Gb1 levels at diagnosis of GD. Classification of mild type 1, severe type 1 and neuronopathic GD (nGD) was based on genotypes. Lyso-Gb1 levels of subjects with wild-type GBA1 were considered to be the control. NS, non-significant. Black dots represent the outliers.

Figure 3

The receiver operating characteristic (ROC) curve was used to evaluate the lyso-Gb1 ability for classifying Gaucher disease vs. no Gaucher disease. The area under the curve (AUC) was calculated.

Figure 4

Lyso-Gb1 levels in subjects with monoallelic variants in GBA1 (carriers) according to the cause for sending a sample; clinical features (clinic), family history of GD (family), Parkinson’s disease (PD), and subjects enrolled on a study of prodromal Parkinson’s disease (research). Lyso-Gb1 levels of subjects with wild-type GBA1 were considered to be the control. Black dots represent the outliers.

Figure 5

Receiver operating characteristic (ROC) curve was used to evaluate the lyso-Gb1 ability for classifying carrier vs. wild-type GBA1. The area under the curve (AUC) was calculated.

Figure 6

Number of patients tested per year over the seven years of study.