A 31-year-old female patient has been diagnosed with bipolar Affective disorder. She is planned to be started on Lithium. Before starting it, which of the following laboratory tests should be done?
**Core Concept**
Before initiating Lithium therapy, it is essential to assess the patient's renal function and thyroid status due to the potential for Lithium to cause nephrotoxicity and thyroid dysfunction. Lithium can impair renal function by reducing glomerular filtration rate (GFR) and increasing the risk of nephrogenic diabetes insipidus. Additionally, Lithium can also affect thyroid function by inhibiting the release of thyroid hormones.
**Why the Correct Answer is Right**
The correct laboratory test to be done before starting Lithium is a **serum creatinine** level to assess the patient's renal function. This is because Lithium is primarily excreted by the kidneys, and impaired renal function can lead to increased Lithium levels, potentially causing toxicity. **Option A** is the correct answer because it assesses the patient's renal function, which is crucial before initiating Lithium therapy.
**Why Each Wrong Option is Incorrect**
* **Option B:** Serum urea level is not a specific indicator of renal function and can be affected by various factors, including dehydration and dietary changes.
* **Option C:** Serum electrolyte levels, including potassium and sodium, may be affected by Lithium therapy, but they are not the primary concern before initiating treatment.
* **Option D:** Hemoglobin A1c (HbA1c) is a measure of glycemic control and is not directly related to Lithium therapy.
**Clinical Pearl / High-Yield Fact**
Lithium levels should be monitored regularly, especially in patients with impaired renal function, as it can increase the risk of toxicity.
**Correct Answer:** A. Serum creatinine level.