The doctor may order any or all of the following tests to ascertain if a person has IBM2:

Blood test for serum Creatine Kinase (CK or CPK);
Nerve Conduction Study (NCS) / Electomyography (EMG);
Muscle Biopsy;
Magnetic Resonance Imaging (MRI) or Computer Tomography (CT) Scan to determine true sparing of quadriceps;
Blood Test or Buccal swab for genetic testing;

Classification
Types of hereditary inclusion body myopathy:

IBM2 is the most common form, and is an autosomal recessive form, caused by mutations in the GNE gene; this form mainly affects leg muscles, but with an unusual distribution that spares the quadriceps. The incidence of this form is about 10 per million per year. There are two forms: a quadriceps sparing myopathy (autosomal recessive form of inclusion body myopathy) and Nonaka type distal myopathy (distal myopathy with rimmed vacuoles). While occurring worldside it is most common in Jews of Persian origin. The GNE gene ecodes the rate-limiting, bifunctional enzyme of sialic acid biosynthesis, uridine diphosphate-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase. Disease occurs when both copies in the genome are non functional. The pathophysiology is still unclear. Cardiac involvement may occur. IBM3 is a sometimes autosomal dominant and sometimes autosomal recessive form caused by mutations in MYHC2A;  it is relatively mild muscle disorder.
Autosomal dominant (IMB3; OMIM 605637 [1]) and autosomal recessive (IBM2; OMIM 600737 [2]) forms have been described. The autosomal recessive form, first characterized in Jews of Persian descent, is a myopathy that affects mainly leg muscles, but with an unusual distribution that spares the quadriceps, so-called quadriceps-sparing myopathy (QSM). This disorder was subsequently found in other Middle Eastern families, the gene was mapped to 9p13-p12, and in 104 affected persons from 47 Middle Eastern families the same mutation in homozygous state was found in the GNE gene. Affected individuals in families of other ethnic origins were found to be compound heterozygotes for other distinct mutations in the GNE gene. From OMIM 603824. [3]

See also
Inclusion body myositis, a more common and non-hereditary form. Valosin-containing protein (VCP); mutations in VCP cause multisystem proteinopathy (MSP) which can present (among others) as a rare form of inclusion body myopathy. References
External links
GeneReviews/NCBI/NIH/UW entry on Inclusion Body Myopathy 2
GeneReviews/NCBI/NIH/UW entry on Inclusion Body Myopathy with Paget Disease of Bone and/or Frontotemporal Dementia