General Guidelines


2. Rather than ordering screening labs, it is more important to make sure your patient is receiving appropriate health maintenance care from a primary care physician. National guidelines for adult preventive care are complicated and are updated yearly. For example, from age 21 to 50, current guidelines recommend that all patients should see their PCP every one to three years; after age 50 it should be annual. Depending on variables such as gender, age, and other risk factors, all your patients should be receiving regular screening tests such as breast exams, pelvic exams and pap tests, fecal occult blood tests, testicular and prostate exams, and skin exams for melanoma. The bottom line is: Don’t fool yourself into believing that you are fulfilling the role of a PCP by simply ordering some lab tests.


The best reason for psychiatrists to routinely order a battery of tests is to provide a baseline in case you need to prescribe a medication that can cause lab abnormalities. Common psychiatric medications can cause abnormalities in the complete blood count (CBC) (anticonvulsants, some antipsychotics), electrolytes (SSRIs, anticonvulsants), kidney functions tests (lithium), thyroid function tests (lithium), lipids (antipsychotics) and liver function tests (anticonvulsants, some antidepressants). Thus, one can argue that you should order this entire battery of tests just in case your patient ends up on one of these meds.


There have been very few studies done to evaluate the utility of this practice. The first comprehensive review (Anfinson TJ et al., Gen Hosp Psychiatry 1992;14:248-257) concluded that screening labs often reveal abnormalities in patients who: 1. Are inpatients, particularly in state hospitals and VAs; 2. Have low socioeconomic status; and 3. Have poor outpatient follow-up. In these populations, the medical problems revealed by screening labs were consequences of poor health care, but were unlikely to be causes of psychiatric illness. Such patients require thorough physical exams, review of systems, and lab testing in order to pick up on a variety of medical problems. But studies focusing on general inpatient units, in which high proportions of patients had private insurance, found much lower rates of clinically significant lab findings, ranging from 0.8% to 4%. Synthesizing all the studies, the authors reported that the most useful tests for a limited screen for inpatients were serum glucose, electrolytes, BUN, creatinine, and urinalysis.


As you can see, the focus of all of these studies is on inpatients, providing little guidance for the majority of psychiatrists, who see primarily outpatients. I found only two studies focusing on outpatients, and both tested the utility of ordering a TSH (thyroid stimulating hormone) in outpatients presenting with major depression. The yield of cases of clinical hypothyroidism was very low. In a series of 200 outpatients with major depression, there were no overt cases of hypothyroidism, and there were 5 (2.6%) cases of “subclinical” hypothyroidism. All patients were treated openly with Prozac, and there was no relationship between response rate and thyroid status (Fava M et al., J Clin Psych 1995 May; 56(5):186-192). In a larger series of 725 geriatric outpatients with depression, only 5 patients (0.7%) had high TSH levels, and patients with elevated TSH did not differ from patients with normal TSH in the severity or symptom pattern of depression (Fraser SA et al., Gen Hosp Psychiatry 2004;26:302-309).


1. For inpatients or outpatients of low SES and low rate of outpatient medical care: Obtain a medical consultation for health care maintenance evaluation; if this is not available in your setting, do your own physical exam, conduct a careful medical review of systems, and order a full battery of screening tests: CBC, electrolytes, BUN, creatinine, glucose, lipid panel, liver function tests, thyroid function tests, B12, urinalysis. For those at higher risk for STDs, order VDRL.


3. For outpatients of higher SES with private insurance: Unless you are planning to start medications that may cause specific lab abnormalities, do not order any labs, and ensure that the patient receives basic recommended health care maintenance visits with a PCP.