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8. Diagnostic Assessment of Schizophrenia
Keywords
DiagnosisDiagnostic criteriaDSM-5ICD-11Diagnostic errorsComprehensive assessmentSymptomsFunctionQuality of lifeRating scalesEssential Concepts
Schizophrenia is a clinical diagnosis you can make if typical symptoms are present long enough and are severe enough in the absence of other causative factors (i.e., drug use, medical illness, or other psychiatric disorders).
Schizophrenia can be reliably diagnosed using criteria-based diagnostic schemes (e.g., DSM-5 or ICD-11). Diagnostic criteria are a mere shadow of the richness of clinical phenomena encountered in patients with schizophrenia.
Psychosis by longitudinal symptom review is key for a diagnosis of schizophrenia and not if the patient is psychotic in your office.
Typical symptoms of schizophrenia are psychosis and negative symptoms, but other symptom domains need to be assessed as well. Organize your dimensional assessment around six symptom clusters (motor, disorganization, paranoid-hallucinatory, negative, cognition, affective).
An outcomes-focused assessment includes three elements: symptoms, function, and quality of life.
The judicious use of screening tools and rating scales can inform clinical care and strengthen your treatment alliance with patients.
“Madness is tonic and invigorating. It makes the sane more sane. The only ones who are unable to profit by it are the insane.” [1]
Henry Miller, American writer, 1891–1980
The syndrome of schizophrenia, as described in the previous chapter, can be reliably diagnosed using criteria such as those developed by the American Psychiatric Association or the World Health Organization [2]. These diagnostic criteria represent a consensus among experts, identifying narrowly defined, core schizophrenia. They are not a comprehensive description of the full breadths of clinical symptoms that you will encounter in patients with schizophrenia (covered in more detail in the respective sections in this book). In this chapter, I provide guidance on (1) how to put together the information gathered in your interview and mental status exam to reach or reject a diagnosis of schizophrenia and (2) how to assess schizophrenia comprehensively, beyond a mere categorical “schizophrenia present of not.”
Diagnosing Schizophrenia for the First Time
All psychiatric disorders are diagnosed by typical symptoms and a typical course only after “organic” factors have been ruled out. Nevertheless, I do not like to call schizophrenia a “diagnosis of exclusion,” as this often implies “by default”; schizophrenia is still diagnosed positively, only if typical signs and symptoms and a typical course are present.
Key Point
Psychosis does not equal to schizophrenia: there are many etiologies of psychosis, with schizophrenia merely one diagnostic possibility. A differential diagnosis to exclude other reasons for psychosis is necessary.
How did psychiatric symptoms develop over time (see Chap. 7) and what symptoms are currently present (see Chaps. 1 and 2)?
Is a delirium present (see Chap. 3)?
Could this be a drug-induced psychosis (see Chap. 4)?
Is one of the secondary schizophrenias responsible for the psychosis (see Chap. 5)?
Are there clinical features more typical for another psychotic disorder, particularly bipolar disorder or psychotic depression (see Chap. 6)?
Diagnostic Criteria
Key diagnostic features of schizophrenia (according to DSM-5)
Active-phase symptoms a |
Core psychotic symptoms |
Delusions |
Hallucinations |
Disorganized speech |
Grossly disorganized behavior or catatonia |
Negative symptoms |
Duration of symptoms |
6 months of illness (including prodrome); 1 month of acute symptoms (unless treated) |
Functional decline |
Required |
As noted earlier, the clinical phenomena are much richer than the diagnostic criteria, so avoid resorting to “checklist psychiatry” in which all you know about schizophrenia is a limited list of symptoms that you check off your clipboard [4], thereby turning a handful of criteria into the real thing of schizophrenia (a problem called reification in epistemology [5]). Those criteria work well to increase the reliability of the terms (two psychiatrists will use the same name for a clinical condition) but do not automatically establish validity of the syndrome of schizophrenia. It will not solve the issue if bipolar disorder and schizophrenia are two separate disorders (dichotomy introduced by Kraepelin) or if they represent two poles of a unitary psychosis (continuum model of psychopathology) [6]. The continued existence of schizoaffective disorder hints at this vexing and unresolved validity problem in psychiatric nosology [7].
Last, as you are searching for diagnostic criteria, keep in mind that sometimes the clinical picture may not overlap well with diagnostic criteria even though the syndrome of schizophrenia would be the best clinical diagnosis for a patient [8]. Conversely, sometimes a patient seems to “meet criteria” (not a phrase I particularly like as it demeans your analytical-synthetic clinical skills) but does not fit clinically. Diagnostic criteria are not a substitute for your clinical judgment. A prototype approach (i.e., matching how close a patient in front of you resembles a prototypical clinical description of a syndrome) may be better suited to capture the complexity of patients [9]. I suspect many clinicians intuitively use a prototype approach together with diagnostic criteria in an iterative process.
Tip
Sometimes you may be trying too hard. Given the limitations of our current knowledge, a best clinical diagnosis and differential diagnoses (working diagnosis) may be all that is possible. Sometimes, the correct diagnosis will emerge over time but not always. Be pleased with diagnosing “schizophrenia spectrum disorder.” The major distinction is toward a truly episodic mood disorder where lithium should be offered.
Confirming Schizophrenia in the Established Patient
You will often take over the care of established patients who come to you on maintenance antipsychotics with a “history of chronic schizophrenia” (Your proverbial “inherited patient”). The basics of confirming a diagnosis of schizophrenia are not different from diagnosing new patients, except that you do not have to reinvent the wheel. Use data already collected for you. During your interview, go for milestones (high school graduation) and clear-cut life events (suicide attempts, psychiatric hospitalizations) to avoid getting bogged down in details that may not help you diagnostically.
Tip
Get collateral information that is both recent and distant. From patients with a long history of schizophrenia, get the first and last hospital discharge summaries to learn how it all started; and also to get a recent view and a chronological summary, if you are lucky. Look for consultation reports; a neurologist might have summarized the history helpfully. Be aware that diagnostic standards and treatments have changed. In the United States, 1980 is a watershed year because of the introduction of a narrow concept of (DSM-III) schizophrenia, also known as the neo-Kraepelinian approach [10].
“He is doing too well for schizophrenia.” This stems from the perception that all patients with schizophrenia must have a chronic, debilitating illness with clear, residual symptoms. This assumption is simply untrue.
The patient is not psychotic when interviewed. I am treating many patients whom I have never seen psychotic because they have stayed on maintenance antipsychotics after their first episode and never have relapsed.
The patient seems to be a good “historian” (a useful, albeit obviously incorrect term unless that patient has a university degree in history [11]) and convinces you that previous psychiatrists were incorrect about the diagnosis. “I never heard voices” is not an uncommon statement where lack of insight into symptoms and poor memory can distort the recollection of past events and internal mental states.
Key Point
Most of the time, most patients with treated schizophrenia are not psychotic or only have minimal symptoms unless they are treatment-refractory. (I admit that there is a bit of circular reasoning here.)
Common Diagnostic Mistakes
Schizophrenia is not diagnosed because of prominent mood symptoms during an exacerbation of schizophrenia, even though mood symptoms are not prominent during the longitudinal course of the illness.
Schizophrenia is not diagnosed because the disorder seems to not have been present long enough (e.g., 6 months in DSM-5). In reality, most patients have been ill for many months or even years ones they reach you. The prodromal period prior to the onset of frank psychosis counts toward illness duration.
Schizophrenia is missed because symptoms are falsely attributed to drug use. Conversely, schizophrenia is diagnosed even though substance use alone can explain the presentation.
Schizophrenia is diagnosed because dissociative symptoms and transient psychotic experiences (e.g., mild paranoid ideation or stress-induced hallucinations) are misinterpreted as evidence for schizophrenia.
“Cultural” explanations are proffered to falsely reject schizophrenia or to inappropriately invoke schizophrenia. In people from other cultures or with other religions, you are occasionally unable to judge if psychosis is present: ask somebody from within the culture in order to avoid misdiagnosis in either direction. However, the syndrome of schizophrenia is usually easily recognizable, regardless of where the patient is from, and the “cultural” aspect is a mere distraction. Anyone who has traveled to other countries and evaluated patients with schizophrenia there will confirm that patients with schizophrenia look strikingly similar. Nevertheless, “pathoplastic” (illness-shaping) influences of culture on diseases and their symptoms can lead to lack of congruity with DSM categories (e.g., bouffée délirante of Haiti: an acute, confusional disorder that resolves quickly – one example of a “culture-bound” syndrome).
Racial stereotypes and fears may bias your diagnostic assessment. Overdiagnosis of schizophrenia in African Americans has been attributed to an overemphasis on psychotic symptoms, while depressive symptoms are missed [12].
The patient is diagnosed with schizophrenia because the patient looks psychiatrically ill even though there is no evidence for psychosis (criteria are not met).
Peculiarities in thinking and in interests are viewed as delusional. Consider the possibility of autism.
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