IGHG3 and neuropathy, small fiber: Nevertheless, the majority of diagnostic tools for LC are under development, such as the use of hyperpolarized magnetic resonance to identify abnormalities of pulmonary gas exchange, imaging to detect microclots or small fiber neuropathy [11,170], while some other tests were also used in patients with ME/CFS and dysautonomia, such as the determination of serum or salivary cortisol, antibodies against herpesviruses, total immunoglobulin concentrations (IgG, IgA, IgM, IgG3), the test for natural killer cell function, tests for orthostatic intolerance, etc. [171].