What lab result indicates the presence of target organ damage in a patient with poorly controlled hypertension?

In the context of poorly controlled hypertension, the presence of target organ damage is essential to assess as it underscores the severity of the condition. A serum creatinine level of 2.6 mg/dL indicates kidney impairment, which is a critical form of target organ damage. The kidneys are highly sensitive to changes in blood pressure; chronic hypertension can lead to nephrosclerosis and ultimately renal failure. An elevated serum creatinine reflects decreased renal function and is a reliable indicator that the kidneys are affected by prolonged high blood pressure.

The other lab results, such as potassium, sodium, and blood glucose levels, do not specifically indicate damage to target organs related to hypertension. While they may reveal other aspects of health or potential complications, they don't provide the same direct evidence of organ damage as elevated creatinine levels do in this situation.