DSM-5 Handbook of Differential Diagnosis is a useful guide, both for those familiar with DSM-5 and for those still learning the ropes. It provides a framework in which to consider patients’ presenting symptoms and history in order to arrive at the correct diagnoses. The book includes a six-step diagnostic process, 29 symptom-based flow-charts, and 66 differential diagnosis tables.
Dr. First begins his presentation of differential diagnosis with the first section, titled Differential Diagnosis Step by Step. He introduces a six-step framework within which to consider diagnoses:
1) Rule out malingering and factitious disorder.
2) Rule out substance etiology.
3) Rule out a disorder due to a general medical condition.
4) Determine the specific primary disorder(s).
5) Differentiate adjustment disorders from the residual other specified or unspecified disorders.
6) Establish the boundary with no mental disorder.
He offers useful tips for each step. For example, under step 2, rule out substance etiology, he breaks it down further. Once the reader has determined that the patient has used a substance, he or she needs to determine whether there is a causal relationship between the substance use and the psychiatric symptoms. To do this, the reader should consider the temporal relationship between substance use and symptoms, whether the pattern and amount of substance use are consistent with the symptoms, and whether other factors might better explain the symptoms. Next, the reader must consider that the substance use may be the consequence of a psychiatric disorder or related sequelae rather than the cause. The reader must also determine whether the psychiatric symptoms and substance use are unrelated to each other. This six-step framework should be kept in mind as one approaches the next two sections of the book.
The second section of the book, titled Differential Diagnosis by the Trees, includes decision trees for 29 symptoms. Clinicians can begin with a patient’s most prominent presenting symptom. Dr. First acknowledges that one might need to use multiple decision trees or make multiple passes through one decision tree because of the frequency of comorbidities. The third section of the book, Differential Diagnosis by the Tables, contains tables for 66 DSM-5 diagnoses. After arriving at a tentative diagnosis, the reader can explore those diagnoses most similar to the one in question. The book includes an appendix with ICD-9-CM and ICD-10-CM codes. It is organized by DSM-5 chapter headings. The book ends with alphabetical indices for the decision trees and the differential diagnosis tables.
To illustrate how the reader might use this handbook, consider the following case, summarized from DSM-5 Clinical Cases (1):
The patient, “Barbara,” is a 51-year-old woman with the chief complaint, “I feel like killing myself.” She endorsed anhedonia and depressed mood for 4 months with worsening symptoms for months, including weight loss due to decreased appetite, insomnia, decreased energy, poor concentration with decreased ability to function at work, and ruminative worry that she had done something wrong at her job that would lead to the death of many dogs (she worked at a dog food processing plant). She had started a regimen of sertraline 1 week previously, initiated by her primary care provider. She denied previous psychiatric history, including any history of hypomania or mania. She normally drank one glass of wine at night and recently increased her consumption to two glasses at night to help with sleep. A physical examination performed by her primary care provider did not identify any underlying medical conditions. Laboratory findings were normal and included results from a complete blood count, blood chemistry and thyroid function tests, and measurement of folate and vitamin B12 levels. A mental status examination was positive for psychomotor agitation, poverty of speech, and perseverative thought processes focused on guilt related to errors the patient believed she made at work. She did not endorse any psychotic symptoms. (1, p. 82)
The reader should first determine whether this patient is malingering or has factitious disorder. He or she can then choose a decision tree based on symptoms. Symptoms one could consider include depressed mood, eating behavior changes, insomnia, and suicidal ideation. Because the most prominent symptom in this case is depressed mood, the reader can start with that decision tree for this symptom (2.10). The first question, whether the depressed mood is due to the physiological effects of a substance (step 2 in the step-by-step framework), can be answered “no.” The patient did report an increase from one to two glasses of wine per night, but this appeared to be related to her symptom of insomnia, started after her depression began, and is not likely to be causal. The next question, whether the depressed mood is due to the physiological effects of a general medical condition (step 3 in the step-by-step framework), can be answered “no” because of a negative workup by the patient’s primary care provider. The remaining boxes in the tree encompass step 4 in the step-by-step framework. The next two boxes establish that the patient meets criteria for a major depressive episode. The answer to the next question, whether she has clinically significant manic or hypomanic symptoms, is “no.” The tree then branches to a question of delusions or hallucinations, to which the answer is “no.” The final question is with regard to the duration of the depressive episode. This patient’s episode is less than 2 years, so she meets criteria for major depressive disorder.
Step 5 in the step-by-step framework is not relevant because the patient meets criteria for major depressive disorder. Step 6 is to establish the boundary with no mental disorder. The patient is clearly distressed with impairment in her functioning.
To confirm the diagnosis of major depressive disorder, the reader can then review the differential diagnosis table (Table 3.4.1) for major depressive disorder. The table includes the following diagnoses: major depressive disorder; bipolar I or bipolar II disorder; depressive disorder due to another medical condition; substance-/medication-induced depressive disorder; persistent depressive disorder (dysthymia); premenstrual dysphoric disorder; disruptive mood dysregulation disorder; schizophrenia, delusional disorder, or schizophreniform disorder; schizoaffective disorder; major or mild neurocognitive disorder due to another medical condition or substance-/medication-induced major or mild neurocognitive disorder; adjustment disorder with depressed mood; bereavement; and nonpathological periods of sadness.
DSM-5 Handbook of Differential Diagnosis may be most useful to students and those less familiar with psychiatric diagnosis. I found reading the book to be a worthwhile experience, but I have not been compelled to use it with an actual patient encounter. Many of the branches in the decision trees are steps that an experienced clinician considers quickly and naturally. While this book certainly covers the changes from DSM-IV to DSM-5, it does not focus on highlighting them, so I would not recommend this book as an efficient way to become familiar with the changes. This would be an excellent book for someone unfamiliar with DSM-IV who is learning psychiatric diagnosis for the first time, for example, a medical student or early psychiatric resident. The six-step framework provides a nice starting place. The decision trees are thorough and meticulous. The differential diagnosis tables offer a nice review of related diagnoses. More experienced clinicians may consider consulting this book to check themselves as they begin to use DSM-5 but will not likely find it necessary or helpful to use it regularly as a diagnostic aid.