The HAS2 variant was previously associated with the characteristic skin folding that is seen in the Chinese Shar-Pei and was postulated to control SPAID as well, described by Olsson et al 2011 (https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1001332).
The digital droplet PCR (ddPCR) assay for absolute copy number quantification of a copy number variant (CNV) in the HAS2 gene is offered through Cornell's Animal Health Diagnostic Center. It is an excellent molecular test, and Cornell is an official research partner or Embark.
However, a more recent publication used whole genome sequencing to define a causative variant in a gene that codes for a pro-inflammatory protein, MTBP. This publication can be found here: Metzger et al, 2017 (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5418765/). They discuss the Olsson publication as well as follow-up work done by the same group, as follows.
"It was proposed that a 16.1 Kb duplication upstream of the hyaluronan synthase 2 (HAS2) on chromosome (CFA) 13, which was detected in Shar-Pei with a padded muzzle (meatmouth type), was associated with skin wrinkling and periodic fever in Shar-Pei dogs [11, 12]. Therefore, this variant was assumed to affect both fever and thick and folded skin . However, a direct relation of specific copy numbers detected by real-time PCR to Shar-Pei fever as an individual phenotype with no regard to other inflammatory signs could not be confirmed . Further investigations of affected Shar-Pei showed that clinical manifestation was much more variable and recurrent bouts of fever were only one of various clinical signs designated now as a syndrome termed Shar-Pei autoinflammatory disease (SPAID). "
The MTBP variant is more heavily supported as having a causal effect on Shar-Pei Autoinflammatory disease, as demonstrated in Metzger et al 2017. It actually occurs in the MTBP gene itself, a gene heavily involved in the inflammatory response, and has been demonstrated to affected protein structure.