Laboratory Investigations in Psychiatry — MCQs
Which is the mood stabilizer with a narrow therapeutic index?
What is the possible cause of irreversible dementia?
What is the most appropriate investigation for a patient with bipolar disorder on lithium therapy for 6 months, who presents with seizures, coarse tremors, confusion, and weakness of the limbs after a day of fasting?
Reversible dementia is seen in?
A female patient has been on lithium for bipolar disorder for 6 months. After fasting for several days due to religious reasons, she presents with seizures, tremors, confusion, and weakness. What is the most appropriate investigation to diagnose her condition?
Among the following, which test is essential in pre-treatment evaluation for lithium therapy:
Slow waves in EEG activity are seen in:
A patient presents with seizures that were controlled with midazolam. Lumbar puncture (LP) revealed no pathology. What is the confirmatory test in the condition shown in the MRI below?
Which of the following are useful investigations for diagnosis of unresponsive endometrium as a cause of primary amenorrhoea? 1. Karyotype 2. Progesterone challenge test 3. Hormonal studies 4. Hysterosalpingography Select the correct answer using the code given below.
What is the first step an epidemiologist takes in an epidemic investigation?
Laboratory Investigations in Psychiatry Indian Medical PG Practice Questions and MCQs
Question 1: Which is the mood stabilizer with a narrow therapeutic index?
- A. lithium (Correct Answer)
- B. valproate
- C. lamotrigine
- D. carbamazepine
Explanation: Correct Option: Lithium - Lithium has a narrow therapeutic index, meaning there is a small difference between therapeutic and toxic doses (therapeutic range: 0.6-1.2 mEq/L; toxic level: >1.5 mEq/L) [1] - This narrow therapeutic window necessitates frequent monitoring of serum lithium levels and careful dosage adjustments to prevent toxicity while maintaining efficacy in mood stabilization [2] - Common signs of lithium toxicity include tremor, confusion, ataxia, and in severe cases, seizures and renal failure Incorrect Option: Valproate - While valproate is an effective mood stabilizer, its therapeutic index is wider compared to lithium, making it generally safer with less stringent monitoring requirements for toxicity [4] - It's associated with adverse effects like hepatotoxicity and pancreatitis, but acute toxicity from minor dose variations is less common than with lithium Incorrect Option: Carbamazepine - Carbamazepine is an anticonvulsant and mood stabilizer with a wider therapeutic index than lithium, though it requires monitoring for drug interactions and hematologic effects (agranulocytosis, aplastic anemia) [3] - Common side effects include dizziness, ataxia, and hyponatremia, but the risk of severe toxicity from minor dose changes is significantly lower than with lithium [3] Incorrect Option: Lamotrigine - Lamotrigine is a mood stabilizer used for bipolar disorder with a relatively wide therapeutic index, especially when compared to lithium - The most concerning side effect is Stevens-Johnson syndrome, a rare but serious skin rash, which risk is increased by rapid dose escalation; requires slow titration
Question 2: What is the possible cause of irreversible dementia?
- A. Vitamin B12 deficiency
- B. NPH
- C. Hypothyroid
- D. Lewy body (Correct Answer)
Explanation: ***Lewy body*** - **Lewy body dementia** is a progressive, irreversible neurodegenerative disorder characterized by the abnormal accumulation of **alpha-synuclein proteins** within neurons [1]. - It presents with fluctuating cognition, recurrent visual hallucinations, and spontaneous **parkinsonism**, eventually leading to severe and irreversible cognitive decline [1]. *Vitamin B12 deficiency* - **Vitamin B12 deficiency** can cause cognitive impairment and dementia-like symptoms, but these are often **reversible** with appropriate B12 supplementation [2]. - Symptoms include **anemia**, peripheral neuropathy, and psychiatric changes, which can improve with treatment. *NPH* - **Normal Pressure Hydrocephalus (NPH)** presents with a classic triad of gait disturbance, urinary incontinence, and dementia [2]. - While it causes dementia, it is often **reversible** with surgical placement of a **ventriculoperitoneal shunt** to drain excess CSF [2]. *Hypothyroid* - **Hypothyroidism** can lead to cognitive slowing, memory impairment, and confusion, resembling dementia. - These symptoms are typically **reversible** and improve significantly with **thyroid hormone replacement therapy**.
Question 3: What is the most appropriate investigation for a patient with bipolar disorder on lithium therapy for 6 months, who presents with seizures, coarse tremors, confusion, and weakness of the limbs after a day of fasting?
- A. Serum Electrolyte
- B. ECG
- C. Serum Lithium (Correct Answer)
- D. Serum creatinine
Explanation: ***Serum Lithium*** - The patient's symptoms (seizures, coarse tremors, confusion, weakness) are classic signs of **lithium toxicity**. - Fasting can lead to **dehydration** and electrolyte imbalances, which can increase lithium levels and precipitate toxicity. *Serum Electrolyte* - While electrolyte imbalances can contribute to lithium toxicity and symptoms, measuring electrolytes alone will not directly confirm **lithium overdose**. - **Hyponatremia** and **dehydration** can exacerbate lithium toxicity by increasing renal reabsorption of lithium. *ECG* - **ECG changes** (e.g., T-wave abnormalities, QTc prolongation) can occur with severe lithium toxicity, but it is not the primary diagnostic test. - ECG is a supportive investigation to assess cardiac complications, not the direct cause of the neurological symptoms. *Serum creatinine* - **Serum creatinine** is important for monitoring **renal function**, as lithium is cleared renally and renal impairment can lead to higher lithium levels. - However, assessing creatinine levels will not directly diagnose acute lithium toxicity; it helps evaluate the **renal health** and potential for toxicity.
Question 4: Reversible dementia is seen in?
- A. Pick's disease
- B. Alzheimer's disease
- C. Hypothyroidism (Correct Answer)
- D. Subacute demyelination of spinal cord
Explanation: ***Hypothyroidism*** - **Hypothyroidism** can lead to cognitive impairment, including memory loss, slowed thinking, and executive dysfunction, which are reversible with appropriate **thyroid hormone replacement therapy**. - This condition is often characterized by other systemic symptoms like fatigue, weight gain, and cold intolerance, which also improve with treatment. *Pick's disease* - **Pick's disease** is a type of **frontotemporal dementia** caused by progressive degeneration of brain cells, primarily in the frontal and temporal lobes. - It is a **neurodegenerative** disorder, meaning it is progressive and irreversible. *Alzheimer's disease* - **Alzheimer's disease** is the most common cause of dementia, characterized by the accumulation of **amyloid plaques** and **neurofibrillary tangles** in the brain [1]. - It is a **progressive and irreversible neurodegenerative disease** with no cure [2]. *Subacute demyelination of spinal cord* - **Subacute demyelination of the spinal cord** typically refers to conditions like **subacute combined degeneration** due to **vitamin B12 deficiency** [1]. - While this can cause neurological symptoms, including cognitive changes, its primary impact is on the spinal cord and peripheral nerves, and "dementia" in the classic sense is not the primary or defining feature of spinal cord demyelination itself, although B12 deficiency can cause broader cognitive issues [1].
Question 5: A female patient has been on lithium for bipolar disorder for 6 months. After fasting for several days due to religious reasons, she presents with seizures, tremors, confusion, and weakness. What is the most appropriate investigation to diagnose her condition?
- A. Serum electrolytes
- B. Serum lithium levels (Correct Answer)
- C. ECG
- D. MRI
Explanation: **Serum lithium levels** - The patient's symptoms (seizures, tremors, confusion, weakness) are classic for **lithium toxicity**. - **Fasting** can lead to dehydration and electrolyte imbalance, which can increase lithium concentrations and toxicity [1]. *Serum electrolytes* - While **electrolyte imbalances** can occur with fasting and contribute to symptoms, measuring serum electrolytes alone will not directly diagnose lithium toxicity. - Electrolyte disturbances might be a predisposing factor or a concomitant issue, but not the primary diagnostic test for lithium toxicity itself [1]. *ECG* - An **ECG** can reveal cardiac effects of lithium toxicity, such as T-wave flattening or inversion, but it is not the most appropriate direct diagnostic test for the condition itself. - ECG changes are secondary manifestations and may not always be present or specific. *MRI* - While an **MRI** of the brain might be considered to rule out other causes of neurological symptoms like a stroke or brain lesion, it is not the initial or most appropriate investigation for suspected lithium toxicity. - The clinical picture strongly points to a pharmacological cause, making laboratory tests more relevant first-line diagnostics than imaging.
Question 6: Among the following, which test is essential in pre-treatment evaluation for lithium therapy:
- A. Fasting blood sugar
- B. Serum creatinine (Correct Answer)
- C. Liver function tests
- D. Platelet count
Explanation: ***Serum creatinine*** - **Lithium** is almost entirely excreted by the kidneys, so baseline renal function assessed by **serum creatinine** and estimated glomerular filtration rate (eGFR) is crucial. - This helps determine the appropriate starting dose and monitor for potential **lithium-induced renal impairment** during therapy. *Fasting blood sugar* - While important for general health screening and monitoring metabolic syndrome, **lithium** does not directly impact glucose metabolism to the extent that it requires pre-treatment evaluation for dosing or safety reasons. - This test is not considered essential specifically for lithium pre-treatment. *Liver function tests* - **Lithium** is not metabolized by the liver, and **hepatotoxicity** is not a known side effect. - Therefore, baseline liver function tests are not considered essential for initiating lithium therapy. *Platelet count* - **Lithium** rarely causes significant hematological abnormalities like **thrombocytopenia** or **thrombocytosis**. - A baseline platelet count is generally not required for pre-treatment evaluation unless there are other clinical indications.
Question 7: Slow waves in EEG activity are seen in:
- A. Delirium (Correct Answer)
- B. Depression
- C. Schizophrenia
- D. Mania
Explanation: **Delirium** - **Generalized slowing** of EEG activity is characteristic of **delirium**, reflecting global brain dysfunction. - This finding is often associated with **encephalopathy**, metabolic disturbances, or drug intoxication. *Depression* - EEG changes in depression are typically **less pronounced** and may involve subtle alterations in alpha rhythm, not widespread slow waves. - Depression is primarily a **mood disorder**, and while it can affect cognitive function, it does not usually cause the global cerebral dysfunction seen in delirium. *Schizophrenia* - EEG findings in schizophrenia are often **non-specific** or involve subtle changes like increased theta activity, but not generalized slow waves. - Schizophrenia is a **psychotic disorder** characterized by thought disturbances, which are not reflected as global EEG slowing. *Mania* - Acute manic episodes are generally associated with **normal EEG activity**, or sometimes increased fast activity. - Mania is a **mood disorder** characterized by elevated energy and mood, distinct from the global cognitive impairment of delirium.
Question 8: A patient presents with seizures that were controlled with midazolam. Lumbar puncture (LP) revealed no pathology. What is the confirmatory test in the condition shown in the MRI below?
- A. PET scan
- B. CBNAAT
- C. MR spectroscopy (Correct Answer)
- D. MRI serial scan
Explanation: ***MR spectroscopy*** - The MRI shows multiple **ring-enhancing lesions**, which, combined with the history of seizures and normal LP, strongly suggests **neurocysticercosis**. - **MR spectroscopy** can detect the specific biochemical markers (e.g., lactate, succinate) within the cyst, which are indicative of the parasitic infection, and can help differentiate it from other lesions like tumors or abscesses. *PET scan* - A **PET scan** primarily assesses metabolic activity and is more commonly used in the evaluation of tumors or neurodegenerative diseases. - It is generally not the primary or confirmatory test for neurocysticercosis, as it does not directly visualize the parasite or its specific biochemical markers. *CBNAAT* - **CBNAAT (Cartridge-Based Nucleic Acid Amplification Test)** is a rapid molecular test primarily used for the diagnosis of **tuberculosis**, not neurocysticercosis. - While tuberculosis can cause CNS lesions, the clinical and imaging presentation (multiple ring-enhancing lesions) is more suggestive of neurocysticercosis, and CBNAAT would not confirm this diagnosis. *MRI serial scan* - **Serial MRI scans** are useful for monitoring the progression or resolution of lesions over time, especially in response to treatment. - However, a serial scan is not a "confirmatory test" for the initial diagnosis; it provides prognostic or follow-up information rather than confirming the etiology.
Question 9: Which of the following are useful investigations for diagnosis of unresponsive endometrium as a cause of primary amenorrhoea? 1. Karyotype 2. Progesterone challenge test 3. Hormonal studies 4. Hysterosalpingography Select the correct answer using the code given below.
- A. 2, 3 and 4
- B. 1, 2 and 3 (Correct Answer)
- C. 1, 2 and 4
- D. 1, 3 and 4
Explanation: ***1, 2 and 3*** - In the workup of primary amenorrhea with suspected **unresponsive endometrium**, a systematic approach is essential to differentiate between end-organ failure and central causes. - **Karyotyping** is important as chromosomal abnormalities like **Turner syndrome (45,X)** can present with primary amenorrhea due to **gonadal dysgenesis**, leading to hypoestrogenism and thus an endometrium that appears "unresponsive" due to lack of estrogen priming, not intrinsic endometrial pathology. - **Progesterone challenge test** is a key diagnostic tool: withdrawal bleeding indicates adequate estrogen and a responsive endometrium; **no bleeding despite adequate estrogen** suggests either true endometrial unresponsiveness (Asherman's syndrome, Müllerian agenesis) or estrogen deficiency. - **Hormonal studies** (FSH, LH, estradiol) are crucial to interpret the progesterone challenge test and distinguish between **hypergonadotropic hypogonadism** (ovarian failure with high FSH/LH), **hypogonadotropic hypogonadism** (low FSH/LH/estrogen), and eugonadal amenorrhea with endometrial factors. *2, 3 and 4* - While **hysterosalpingography (HSG)** can visualize structural uterine abnormalities (Asherman's syndrome, Müllerian anomalies), it is typically performed **after** initial hormonal assessment. - This option excludes **karyotyping**, which is essential in the initial evaluation of primary amenorrhea to rule out chromosomal causes that present with hypoestrogenism and secondary endometrial unresponsiveness. - The systematic approach starts with hormonal evaluation and progesterone challenge before proceeding to imaging studies. *1, 2 and 4* - This option excludes **hormonal studies**, which are fundamental to the diagnostic algorithm. - Without FSH, LH, and estradiol levels, it is impossible to properly interpret a progesterone challenge test or determine whether the "unresponsive endometrium" is due to estrogen deficiency, ovarian failure, or true endometrial pathology. - Hormonal studies guide the next steps in investigation and management. *1, 3 and 4* - This option excludes the **progesterone challenge test**, which is a simple, cost-effective screening test to assess estrogen status and endometrial responsiveness. - While HSG provides anatomical information, the progesterone challenge test is typically performed earlier in the diagnostic algorithm to determine if further invasive imaging is warranted. - A systematic hormonal evaluation with progesterone challenge should precede invasive procedures like HSG.
Question 10: What is the first step an epidemiologist takes in an epidemic investigation?
- A. Confirm the diagnosis (Correct Answer)
- B. Identify the prone people
- C. Identify the causative factors
- D. Identify the cases
Explanation: ***Confirm the diagnosis*** - The initial and most crucial step is to **confirm the diagnosis** of the disease in question to ensure that the reported cases are indeed suffering from the same condition. - This step helps to avoid misclassification and ensures the investigation focuses on a specific, confirmed health problem. *Identify the cases* - While essential, **identifying cases** usually follows initial diagnostic confirmation, as you need a clear case definition based on a confirmed diagnosis to correctly identify who is a case. - This involves defining who is considered a case based on symptoms, laboratory results, and epidemiological links. *Identify the prone people* - **Identifying prone people** refers to determining the population at risk, which is a subsequent step after understanding the confirmed disease and its initial pattern. - This step typically falls under characterizing the distribution of the disease (person, place, time) in the investigation. *Identify the causative factors* - **Identifying causative factors** is a later stage in the investigation, often involving analytical studies to test hypotheses, which can only occur effectively once the diagnosis is confirmed and cases are clearly defined and counted. - This step aims to understand *why* the epidemic is occurring, after establishing *what* is occurring.
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