Table 4.

Diagnostic tests and differential diagnosis

Diagnostic tests	Possible diagnosis to be identified
CBC with differential	Leukemia, Evans syndrome
Reticulocytes	FA, DC, SDS, MDS
Smear review	WAS, XLT, BSS, X-linked gray plt syndrome, gray plt syndrome, MYH9-RD, RUNX1 heterozygous, leukemia
Immunoglobulins (IgM, IgG, IgA)	CVID, WAS
Liver Function Tests	Hepatitis C
Infectious work-up: CMV, HIV PCR	Infectious-associated thrombocytopenia
H pylori stool antigen/urea breath test	H pylori–associated thrombocytopenia
Flow cytometry for lymphocyte subsets	ALPS, WAS, CLL, HIV
ESR, CRP	SLE, other inflammatory causes
ANA, dsDNA	SLE, other inflammatory causes
Bone marrow aspirate/biopsy/cytogenetics	MDS, FA, CAMT, DC, SDS, CLL
Genetic testing: whole-genome sequencing vs specific panels	WAS, XLT, BSS, TAR, X-linked gray plt syndrome, disorders of filamin A, MYH9-RD, vWF type IIb, plt-type vWD, RUNX1 heterozygous, FA, CAMT, DC, SDS, MDS, ALPS
Telomere length	DC
DEB, MMC	FA
Stool elastase, trypsinogen	SDS
Serum trypsinogen, isoamylase	SDS
Plt aggregation	BSS, vWF type IIb, plt-type vWD, RUNX1 heterozygous
vWD panel	vWF type IIb, plt-type vWD

ANA, anti-nuclear antibody; BSS, CAMT, congenital amegakaryotic thrombocytopenia; CRP; C-reactive protein; DEB, diepoxybutane test; dsDNA, double-stranded DNA; ESR, erythrocyte sedimentation rate; MMC, mitomycin C; PCR, polymerase chain reaction; Plt/plt, platelets; RUNX1, RUNT-related transcription factor 1; SDS, Shwachman-Diamond syndrome; SLE, systemic lupus erythematosus; TAR, thrombocytopenia absent radii syndrome; vWD, von Willebrand disease; vWF, von Willebrand factor; WAS, Wiskott-Aldrich syndrome; XLT, X-linked thrombocytopenia