When Klinefelter syndrome is suspected based on clinical examination and preliminary tests, the diagnosis is confirmed by a chromosome analysis test performed using a peripheral blood sample taken from the patient's arm. This test involves examining blood cells to determine the chromosomal structure, and obtaining the results may take a certain amount of time. While 80-90% of individuals with Klinefelter syndrome typically exhibit a 47,XXY chromosomal structure, rarer mosaic types, variants, or structural X chromosome anomalies may also be observed in the remaining cases.