Foundations & Baselines - Lab Test Logic
- Rule out organic conditions mimicking psychiatric symptoms.
- Establish pre-treatment baselines for psychotropic medications.
- Monitor adverse drug reactions (ADRs), therapeutic drug levels.
- Screen for comorbid substance use.
| Test | Indication | Clinical Significance |
|---|---|---|
| CBC | General health; clozapine baseline/monitoring | Anemia, infection; Clozapine: agranulocytosis (monitor ANC) |
| LFTs | Valproate, carbamazepine, alcohol use | Liver function, drug-induced hepatitis, enzyme changes |
| KFTs (RFTs) | Lithium baseline/monitoring, elderly | Renal function assessment; Lithium toxicity risk |
| TFTs (TSH) | Mood/anxiety symptoms, lithium use | Thyroid dysfunction (can mimic psychiatric disorders) |
| Glucose | Antipsychotics (metabolic syndrome risk) | Diabetes mellitus, impaired glucose tolerance |
| Lipids | Antipsychotics, cardiovascular risk assessment | Dyslipidemia, ↑CV risk |
| UDS | Suspected substance use, unexplained symptoms | Detects illicit drugs, medication adherence check |
| ECG | Pre-TCAs, some antipsychotics (QTc), elderly | Arrhythmias, QTc prolongation, baseline cardiac status |
Organic Mimics Hunt - Diagnostic Detectives
📌 Organic psychosis/delirium causes: DIM TOPS (Drugs, Infection, Metabolic, Trauma, Oxygen, Post-ictal, Seizures).
| Medical Condition | Key Psychiatric Symptoms | Relevant Lab Tests |
|---|---|---|
| Hypothyroidism | Depression, cognitive slowing, fatigue | TSH (↑), Free T4 (↓) |
| Hyperthyroidism | Anxiety, agitation, psychosis | TSH (↓), Free T3/T4 (↑) |
| Vit B12 Deficiency | Depression, psychosis, cognitive decline | Serum Vit B12 (↓), MMA (↑) |
| Neurosyphilis | Mania, psychosis, dementia | Serum VDRL/RPR; CSF-VDRL, TPPA |
| Wilson's Disease | Depression, psychosis, personality Δ, parkinsonism | Serum ceruloplasmin (↓), 24-hr urinary Cu (↑) |
| Acute Porphyria | Acute psychosis, anxiety, delirium, abdominal pain | Urine porphobilinogen (PBG) (↑ during attacks) |
Drug Dose Dialing - TDM Targets
TDM optimizes efficacy & minimizes toxicity for select psychotropics.
| Drug | Indication for TDM | Therapeutic Range | Toxic Level | Key Monitoring Points/Frequency |
|---|---|---|---|---|
| Lithium | Narrow index, toxicity, non-response | 0.6-1.2 (acute); 0.4-1.0 mEq/L (maint.) | >1.5 mEq/L | Renal, Thyroid q6-12mo; Levels q3-6mo (stable) |
| Valproate | Toxicity, non-response, adherence | 50-125 µg/mL | >150 µg/mL | LFTs, CBC periodically; Ammonia if symptomatic |
| Carbamazepine | Narrow index, interactions, toxicity | 4-12 µg/mL | >15 µg/mL | CBC, LFTs, Na+; HLA-B*1502 (Asians for SJS risk) |
| Clozapine | Toxicity, poor response, smoking change | >350 ng/mL (efficacy) | >600 ng/mL (seizures) | WBC/ANC (protocol); ECG, EEG, metabolic |
| TCAs (Nortriptyline) | Narrow index, elderly, toxicity, non-response | 50-150 ng/mL | >500 ng/mL (combined) | ECG (QTc); Levels 12h post-dose |
Brain Peeks & Pulses - Neuro-Tools Overview
Structural (CT/MRI) & functional (EEG) brain investigations. Used when initial labs are unrevealing or specific neurological concerns arise.
-
CT/MRI Brain Indications:
- New-onset psychosis (esp. late-onset)
- First manic episode
- Cognitive decline/dementia workup
- Focal neurological signs
- Head trauma with psychiatric sequelae
- Suspected organic brain lesion (e.g., SOL)
- Movement disorders (e.g., Wilson's)
-
EEG Indications:
- Suspected seizures/epilepsy
- Delirium/encephalopathy workup
- Unexplained catatonia
- Monitoring drug-induced seizure risk (e.g., clozapine)
- Sleep disorder assessment (polysomnography)
- Evaluating dissociative episodes
⭐ For a first psychotic episode, structural neuroimaging (CT/MRI) is vital to exclude organic causes.
High‑Yield Points - ⚡ Biggest Takeaways
- Baseline labs (CBC, LFT, KFT, TFT, glucose, lipids) are key before starting psychotropics.
- Lithium: Monitor serum levels (0.6-1.2 mEq/L), TFT, KFT.
- Clozapine: Strict WBC/ANC monitoring for agranulocytosis risk.
- Valproate/Carbamazepine: Check LFTs, CBC; watch for hepatotoxicity, blood dyscrasias, hyponatremia (CBZ).
- Atypical antipsychotics: Monitor for metabolic syndrome (glucose, lipids, weight).
- Urine Drug Screen (UDS): Essential for substance use or acute psychosis.
- Neuroimaging (CT/MRI): For new-onset/atypical psychosis or neurological signs.
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