OVERVIEW

Modern-day psychiatrists have many tools to help make a diagnosis and to treat patients effectively. While the heart of psychiatric diagnosis remains a careful interview and mental status examination (MSE) (while paying close attention to physical findings), laboratory tests (including blood work, neuroimaging, and an electroencephalogram [EEG]) are important adjuncts. These modalities help reveal medical and neurological causes of psychiatric symptoms, as well as aid in the monitoring and progression of certain diseases. They are often of particular benefit in populations (including the elderly, the chronically medically ill, substance abusers, and the indigent) at high risk for medical co-morbidity. Laboratory tests are also commonly used to check blood levels of psychotropic medications and to predict potential side effects. This chapter will focus on the role of a wide array of specific serum, urine, and cerebrospinal fluid (CSF) tests, as well as several diagnostic modalities (e.g., the EEG and neuroimaging), with an emphasis on the strategy and rationale for choosing when to order and how to use the data derived from particular studies. Genetic and biological markers will be discussed in subsequent chapters.

A GENERAL APPROACH TO CHOOSING LABORATORY TESTS AND DIAGNOSTIC STUDIES

Diagnoses in psychiatry are primarily made by the identification of symptom patterns, that is, by clinical phenomenology, as outlined in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR).¹ In this light, the initial approach to psychiatric assessment consists of a thorough history, a comprehensive MSE, and a focused physical examination. Results in each of these arenas guide further testing. For example, historical data and a review of systems may reveal evidence of medical conditions, substance abuse, or a family history of heritable conditions (e.g., Huntington’s disease)—each of these considerations would lead down a distinct pathway of diagnostic evaluation. A MSE that uncovers new-onset psychosis or delirium opens up a broad differential diagnosis and numerous possible diagnostic studies from which to choose. Findings from a physical examination may provide key information that suggests a specific underlying pathophysiological mechanism and helps hone testing choices. Although routine screening for new-onset psychiatric illness is often done, consensus is lacking on which studies should be included in a screening battery. In current clinical practice, tests are ordered selectively with specific clinical situations steering this choice. While information obtained in the history, the physical examination, and the MSE is always the starting point, subsequent sections in this chapter address tests involved in the diagnostic evaluation of specific presentations in further detail.

ROUTINE SCREENING

Decisions regarding routine screening for new-onset psychiatric illness involve consideration of the ease of administration, the clinical implications of abnormal results, the sensitivity and specificity, and the cost of tests. Certain presentations (such as age of onset after age 40 years, a history of chronic medical illness, or the sudden onset or rapid progression of symptoms) are especially suggestive of a medical cause of psychiatric symptoms and should prompt administration of a screening battery of tests. In clinical practice, these tests often include the complete blood cell count (CBC); serum chemistries; urine and blood toxicology; levels of vitamin B₁₂, folate, and thyroid-stimulating hormone (TSH); and rapid plasma reagent (RPR). Liver function tests (LFTs), urinalysis, and chest x-ray are often obtained, especially in patients at high risk for dysfunction in these organ systems or in the elderly. A pregnancy test is helpful in women of childbearing age, from both a diagnostic and treatment-guidance standpoint. Table 3-1 outlines the commonly used screening battery for new-onset psychiatric symptoms. The following sections will move from routine screening to a more tailored approach of choosing a diagnostic workup that is based on specific signs and symptoms and a plausible differential diagnosis.

Table 3-1 Commonly Used Screening Battery for New-Onset Psychiatric Symptoms

PSYCHOSIS AND DELIRIUM

New-onset psychosis or delirium merits a broad and systematic medical and neurological workup. Table 3-2² outlines the wide array of potential medical causes of such psychiatric symptoms. Some etiologies include infections (both systemic and in the central nervous system [CNS]), CNS lesions (e.g., stroke, traumatic bleed, or tumors), metabolic abnormalities, medication effects, intoxication or states of withdrawal, states of low perfusion or low oxygenation, seizures, and autoimmune illnesses. Given the potential morbidity (if not mortality) associated with many of these conditions, prompt diagnosis is essential. A comprehensive, yet efficient and tailored approach to a differential diagnosis involves starting with a thorough history, supplemented by both the physical examination and MSE. Particular attention should be paid to vital signs and examination of the neurological and cardiac systems. Table 3-3³ provides an overview of selected physical findings associated with psychiatric symptoms. Based on the presence of such findings, the clinician then chooses appropriate follow-up studies to help confirm or refute the possible diagnoses. For example, tachycardia in the setting of a goiter suggests possible hyperthyroidism and prompts assessment of thyroid studies (Figure 3-1).⁴ On the other hand, tachycardia with diaphoresis, tremor, and palmar erythema, along with spider nevi, is suggestive of both alcohol withdrawal and stigmata of cirrhosis from chronic alcohol use (Figure 3-2).⁵ The astute clinician would treat for alcohol withdrawal and order laboratory tests (including LFTs, prothrombin time [PT]/international normalized ratio [INR], and possible abdominal imaging), in addition to the screening tests already outlined in Table 3-1. Neuroimaging is indicated in the event of neurological findings, although many would suggest that brain imaging is prudent in any case of new-onset psychosis or acute mental status change (without a clear cause). An EEG may help to diagnose seizures or provide a further clue to the diagnosis of a toxic or metabolic encephalopathy. A lumbar puncture (LP) is indicated (after ruling out an intracranial lesion or an increased intracerebral pressure) in a patient who has fever, headache, photophobia, or meningeal symptoms. Depending on the clinical circumstances, routine CSF studies (e.g., the appearance, opening pressure, cell counts, levels of protein and glucose, culture results, and a Gram stain), as well as specialized markers (e.g., antigens for herpes simplex virus, cryptococcus, and Lyme disease; a cytological examination for malignancy; and acid-fast staining for tuberculosis), should be ordered. A history of risky sexual behavior or of intravenous (IV) or intranasal drug use makes testing for infec-tion with the human immunodeficiency virus (HIV) (with appropriate consent) and hepatitis C especially important. Based on clinical suspicion, other tests might include an antinuclear antibody (ANA) and an erythrocyte sedimentation rate (ESR) for autoimmune diseases (e.g., systemic lupus erythematosus [SLE], rheumatoid arthritis [RA]), ceruloplasmin (that is decreased in Wilson’s disease), and levels of serum heavy metals (e.g., mercury, lead, arsenic, and manganese). Table 3-4⁶ provides an initial approach to the diagnostic workup of psychosis and delirium. Specific studies will be further discussed based on an organ-system approach to follow.

Table 3-2 Medical and Neurological Causes for Psychiatric Symptoms

Table 3-3 Selected Findings on the Physical Examination Associated with Neuropsychiatric Manifestations

Figure 3-1 Thyroid pathology in hyperthyroidism with diffuse goiter.

(Source: Netter Anatomy Illustration Collection, © Elsevier Inc. All rights reserved.)

Figure 3-2 Gross features of cirrhosis of the liver.

(Source: From Netter Anatomy Illustration Collection, © Elsevier Inc. All rights reserved.)

Table 3-4 Approach to the Evaluation of Psychosis and Delirium

ANXIETY DISORDERS

Medical conditions associated with new-onset anxiety are associated with a host of organ systems. For anxiety, as with other psychiatric symptoms, a late onset, a precipitous course, atypical symptoms, or a history of chronic medical illness raises the suspicion of a medical rather than a primary psychiatric etiology. Table 3-5⁷ lists many of the potential medical etiologies for anxiety. These include cardiac disease (including myocardial infarction [MI] and mitral valve prolapse [MVP]); respiratory compromise (e.g., chronic obstructive pulmonary disease [COPD], asthma exacerbation, pulmonary embolism, pneumonia, and obstructive sleep apnea [OSA]); endocrine dysfunction (e.g., of the thyroid or parathyroid); neurological disorders (e.g., seizures or brain injury); or use or abuse of drugs and other substances. Less common causes (e.g., pheochromocytoma, acute intermittent porphyria, and hyperadrenalism) should be investigated if warranted by the clinical presentation. See Table 3-5 for the appropriate laboratory and diagnostic tests associated with each of these diagnoses.

Table 3-5 Medical Etiologies of Anxiety with Diagnostic Tests

MOOD DISORDERS

While depression may be a primary psychiatric disorder, it is also associated with medical conditions. Clinical findings suggestive of thyroid dysfunction, Addison’s disease or Cushing’s disease, pituitary adenoma, neurodegenerative disorders, SLE, anemia, or pancreatic cancer should guide further testing. Workup of these conditions is described below. The new onset of mania merits a full medical and neurological evaluation on a par with that of psychosis and delirium as previously described. While not every diagnostic test and its potential manifestation are discussed here, the following sections provide a more comprehensive system-driven approach to such a diagnostic workup.

METABOLIC AND NUTRITIONAL

Myriad metabolic conditions and nutritional deficiencies are associated with psychiatric manifestations. Table 3-6⁸ provides a list of metabolic tests with their pertinent findings associated with neuropsychiatric dysfunction. Metabolic encephalopathy should be considered in the event of abrupt changes in one’s mental status or level of consciousness. The laboratory workup of hepatic encephalopathy (which often manifests as delirium with asterixis) may reveal elevations in LFTs (e.g., aspartate aminotransferase [AST] and alanine aminotransferase [ALT]), bilirubin (direct and total), and ammonia. Likewise, the patient with uremic encephalopathy generally has an elevated blood urea nitrogen (BUN) and creatinine (consistent with renal failure). Acute intermittent porphyria (AIP) is a less common, yet still important, cause of neuropsychiatric symptoms (including anxiety, mood lability, insomnia, depression, and psychosis). This diagnosis should be considered in a patient who has psychiatric symptoms in conjunction with abdominal pain or neuropathy. When suggestive neurovisceral symptoms are present, concentration of urinary aminolevulinic acid (ALA), porphobilinogen (PBG), and porphyrin should be measured from a 24-hour urine collection. While normal excretion of ALA is less than 7 mg per 24 hours, during an attack of AIP urinary ALA excretion is markedly elevated (sometimes to more than 10 times the upper limit of normal) as are PBG levels. In severe cases, the urine looks like port wine when exposed to sunlight due to a high concentration of porphobilin.

Table 3-6 Metabolic and Hematological Tests Associated with Psychiatric Manifestations

Test	Pertinent Findings
Alanine aminotransferase (ALT)	Increased in hepatitis, cirrhosis, liver metastasis
	Decreased with pyridoxine (vitamin B6) deficiency
Albumin	Increased with dehydration Decreased with malnutrition, hepatic failure, burns, multiple myeloma, carcinomas
Alkaline phosphatase	Increased with hyperparathyroidism, hepatic disease/metastases, heart failure, phenothiazine use Decreased with pernicious anemia (vitamin B12 deficiency)
Ammonia	Increased with hepatic encephalopathy/failure, gastrointestinal bleed, severe congestive heart failure (CHF)
Amylase	Increased with pancreatic disease/cancer
Aspartate aminotransferase (SGOT/AST)	Increased with hepatic disease, pancreatitis, alcohol abuse
Bicarbonate	Increased with psychogenic vomiting Decreased with hyperventilation, panic, anabolic steroid use
Bilirubin, total	Increased with hepatic, biliary, pancreatic disease
Bilirubin, direct	Increased with hepatic, biliary, pancreatic disease
Blood urea nitrogen	Increased with renal disease, dehydration, lethargy, delirium
Calcium	Increased with hyperparathyroidism, bone metastasis, mood disorders, psychosis Decreased with hypoparathyroidism, renal failure, depression, irritability
Carbon dioxide	Decreased with hyperventilation, panic, anabolic steroid abuse
Ceruloplasmin	Decreased with Wilson’s disease
Chloride	Decreased with psychogenic vomiting Increased with hyperventilation, panic
Complete blood count (CBC)
• Hemoglobin, hematocrit • White blood cell count • Platelets • Mean corpuscular volume • Reticulocyte count	Decrease associated with depression and psychosis Only gold members can continue reading. Log In or Register to continue Share this: Click to share on Twitter (Opens in new window) Click to share on Facebook (Opens in new window) Related Related posts: 31: Psychiatric Illness during Pregnancy and the Postpartum Period 39: Personality and Personality Disorders 85: The Role of Psychiatrists in the Criminal Justice System 93: International Psychiatry in the Twenty-First Century 27: Drug Addiction 63: Genetics and Psychiatry Stay updated, free articles. Join our Telegram channel Join Tags: Massachusetts General Hospital Comprehensive Clinical Psychiatry Jun 8, 2016 | Posted by admin in PSYCHIATRY | Comments Off on 3: Laboratory Tests and Diagnostic Procedures Full access? Get Clinical Tree Get Clinical Tree app for offline access Get Clinical Tree app for offline access