Front Matter

Judicious use of the laboratory improves patient care in psychiatry and behavioral science just as it does in internal medicine and other specialties. Laboratory testing is only one component of the complete psychiatric evaluation, which also includes a history, review of systems, functional assessment, and physical and mental status examinations. When lab results are reviewed in the context of the patient’s family history, personal history, lifestyle, and particular exam findings, there is less likelihood of overreacting to a result that may turn out to be inconsequential or even spurious. For example, with an isolated elevation in one test such as alanine transaminase and in the absence of any clinical evidence of disease, the test should simply be repeated and further workup performed only if a twofold or greater elevation persists. When laboratory findings are unclear or present questions, clinical laboratory staff can be an excellent resource for clinicians in the interpretation of test data and in planning further diagnostics. The reference ranges cited in this manual are only general guides, as few reference ranges apply across laboratories and testing methods. Reference intervals supplied by the local laboratory always supersede the intervals suggested here.

What constitutes standard laboratory screening for psychiatric patients in general is not well established. There does appear to be general agreement that a screening laboratory evaluation is indicated for the following patients: those presenting for the first time with major psychiatric syndromes (e.g., psychosis or major mood disorders), elderly patients admitted to the hospital, patients who are undernourished or significantly dehydrated, those with alcohol or drug dependence, and those with delirium or initial presentation of dementia.

Patients admitted to inpatient psychiatry services may undergo the following laboratory evaluation upon admission:

For patients who are at risk of the metabolic syndrome, or those who are to be started on an atypical antipsychotic or other drug associated with this syndrome, the following may be added:

Thyroid-stimulating hormone may be checked for patients presenting with mood disorders or significant anxiety, and for all females age 50 years and older unless testing was done within the past year. Urine or serum pregnancy testing may be performed if there is any question of pregnancy. More extensive laboratory testing may be indicated for patients presenting with syndromes such as acute psychosis, as discussed in the Diseases and Conditions chapter.

Inpatient psychiatrists and those working in research settings may be required to obtain and provide preliminary interpretation of electrocardiogram (ECG) tracings. The ECG is therefore covered in some depth in the Laboratory Tests chapter (including indications, critical and abnormal findings, and typical ECG findings associated with psychotropic medications) and in Appendix C (which includes a table listing 10 rules for a normal ECG, a figure depicting ECG waves and intervals, a figure depicting different degrees of heart block, and a gateway to the evaluation of 10-year cardiac risk using a tool developed by the American College of Cardiology). Other cardiac-related entries appear in the Diseases and Conditions chapter.

The largest component of the Laboratory Tests chapter involves blood chemistries. These are the laboratory tests most often found to be abnormal in patients seen in psychiatric consultation in the general hospital. Abnormalities of blood chemistry often contribute to delirium, anxiety, depression, and other common psychiatric presentations. Chemistry tests that are not yet clinically available are not included.

Cerebrospinal fluid (CSF) tests include amyloid-β_1-42, CSF analysis, cell count and differential, cytology, glucose, lactate, protein, and tau protein. These tests may be useful in the diagnosis of Alzheimer’s disease, encephalitis, meningitis, and other neuropsychiatric disorders. For those who may be interested, several excellent video presentations showing in detail how the lumbar puncture is performed are available online (e.g., on YouTube).

The number of genetic tests currently available is very large, but most test for relatively rare conditions and thus are not included here. Genetic tests that are covered include apolipoprotein E (ApoE) genotyping, cytochrome P450 (CYP450) genotyping, fragile X (FMR1) mutation analysis, HTT mutation analysis for Huntington’s disease, and 5-HTTLPR polymorphism in the serotonin transporter gene SLC6A4. For most clinicians, genetic tests are laboratory send-outs. It is important to inquire directly with the receiving laboratory about costs before sending samples, because these tests may not be covered by insurance and can be prohibitively expensive.

Basic hematology is relevant to psychiatric practice not only because hematological abnormalities may underlie symptoms such as fatigue, inattention, and restless legs but also because psychotropic medications may significantly affect hematological values. In addition to clozapine, many other psychotropic drugs can cause hematological abnormalities. DRESS (drug reaction with eosinophilia and systemic symptoms) is one example that is increasingly recognized with psychotropics such as valproate and lamotrigine.

Structural imaging is a core component of the diagnostic workup for a variety of conditions, particularly those at the interface of psychiatry and neurology. Structural imaging is indicated when signs and symptoms of a major psychiatric disorder first become manifest, for atypical presentations, for atypical age at onset, or for psychiatric symptoms associated with a focal neurological examination.

Because behavioral health clinicians often work in tandem with neurologists, neurosurgeons, and internists, they may find themselves in a position to order or suggest a variety of imaging studies, to assist patients in understanding study results, and to facilitate tests and procedures. Thus, the information related to imaging in this manual covers an array of services—not only neuroimaging but also basic studies such as a chest X-ray and bone mineral density (DEXA) scan. Other imaging tests covered in this manual include angiography, carotid ultrasound, CT, CT angiography, functional MRI, mammography, magnetic resonance angiography, magnetic resonance spectroscopy, MRI, PET, and SPECT. Appendix B includes a table listing signal appearances for various tissues on CT and MRI T1 and T2 scans, along with a description of the steps involved in reading a head CT scan.

Specific infectious diseases encountered in neuropsychiatric practice that are covered in the Diseases and Conditions chapter of this manual include brain abscess, Creutzfeldt-Jakob disease, encephalitis (including arbovirus encephalitis and herpes simplex encephalitis), hepatitis, HIV/AIDS, Lyme disease, meningitis, infectious mononucleosis, progressive multifocal leukoencephalopathy, syphilis and neurosyphilis, tuberculosis, and urinary tract infection. Related entries in the Laboratory Tests chapter include hepatitis panel, HIV testing, Lyme antibodies, syphilis testing, and tuberculosis testing.

The Laboratory Tests chapter of this manual includes information about drug level testing for a selected group of medications, including benzodiazepines, clozapine, and mood stabilizers. The Psychotropic Medications: Laboratory Screening and Monitoring chapter covers what have come to be called “safety labs” for monitoring adverse effects of psychotropic medications, as well as screening lab tests used to obtain baseline values and to ensure that medications can safely be started. Appendix A presents a table of therapeutic and toxic drug levels for commonly used psychotropic medications.

In general, drug levels can be obtained for any drug to confirm toxicity or document noncompliance (with very low levels). Therapeutic ranges are included in this manual for many drugs. Free drug levels may be used in place of total drug levels when the patient has hypoalbuminemia, which can affect the interpretation of total drug levels.

Tests for blood in stool are included because certain psychotropic medications cause occult gastrointestinal bleeding, an underdiagnosed problem in psychiatry. In addition to the fecal occult blood test, a newer test for occult blood—the fecal immunochemical test—is described.

Routine urinalysis provides a great deal of information about general health and genitourinary function. Individual components of the urinalysis are discussed separately to deal with the many implications of individual urine test abnormalities. These components include urine appearance, bilirubin, blood or hemoglobin, casts, color, crystals, epithelial cells and casts, glucose, ketones, leukocyte esterase, microalbumin, nitrite, pH, protein, red blood cell counts and casts, specific gravity, white blood cell counts and casts, and urobilinogen.