We report that informant-gathered information on individuals with a major mental illness can identify most severe lifetime Diagnostic and Statistical Manual (DSM) diagnosis. The notable diagnostic exceptions are generalized anxiety disorder, agoraphobia without panic disorder, alcohol abuse, alcohol dependence and drug dependence, for which there was a moderate level of disagreement between the subject and NOK. Psychiatric symptoms experienced in the last week and childhood trauma scores were concordant between the subject and his or her NOK. Although the ICC for the Barratt Impulsiveness Scale was low, the mean scores were found to be statistically equivalent.
The reliability of psychiatric diagnoses in living individuals generated by a variety of instruments has been demonstrated by the SCID-I (Structured Clinical Interview for Axis-1),22
SCID-II (Structured Clinical Interview for Axis-2),23
and Diagnostic Interview for Genetic Studies.24
However, there is very limited information regarding the reliability of retrospective diagnoses, especially as they apply to post-mortem research. The general approach to establish post-mortem psychiatric diagnoses includes a review of medical records and conducing a psychological autopsy about the decedent with the NOK (). Sundqvist et al.25
reported a kappa coefficient of agreement for diagnoses solely from chart review between the ante and post-mortem diagnoses ranging from 0.35 for schizoaffective disorder to 0.95 with major depression. The inclusion of an interview with the NOK, in addition to the review of medical records, increases the information reliability across diagnostic classifications. Most research of this type relies on using a semistructured information gathering process to organize medical and psychological autopsy material. The two common ones are the Diagnostic Interview After Death,26, 27
Diagnostic Instrument for Brain Studies28
and their variants.29, 30
Previously published reliability assessments for post-mortem diagnoses
Deep-Scoboslay et al.
Kelly and Mann32
and Lehrmann et al.33
used SCID-P (axis 1) and the SCID-II with either DSM-III-R and DSM-IV criteria. They combined this information with antemortem data organized through the Diagnostic Interview After Death and found the instruments demonstrate good reliability when compared with medical records. This study also shows good reliability of informant information for a majority of diagnoses. Because our sample was limited to primary diagnoses of mood disorders, the reliability determination of the other diagnoses such as schizophrenia was incomplete. For example, three subjects endorsed generalized anxiety disorder symptoms and two post-traumatic disorder symptoms but these symptom sets were not observed by the NOK. The subject–NOK interview provided the greatest discordance in the alcohol use disorders with four subjects reporting misuse but not by the NOK. This is consistent with the clinical experience of patients often under reporting their drinking. There was higher concordance with drug use, but the frequency of any positive response was low with only three NOK or subject reported misuse. Lehrmann et al.33
looked at substance misuse in a post-mortem sample identified by medical examiner records, NOK interviews and toxicology. They showed that when medical records and toxicology data are combined, the detection rate drastically increases. Clearly, increasing the number of sources of information allows for greater reliability for all diagnoses. Two other studies looked at the concordance between psychiatric diagnosis generated by an informant compared with that of a subject and found high concordance.34, 35
Schneider et al.34
found kappa correlation coefficients for mood disorders at 0.79, anxiety at 0.79 and any personality disorder at 0.92, which are comparable to our findings. Zhang et al.35
also found high concordance with SCID-based diagnosis and also conducted a Ham-D with a subject and two informants. They found that the results were significantly correlated (Spearman's rho=0.57). Their results had substantially higher concordance than we report and this is most likely because they used two informants for each subject.
Genetic and family studies using the family history method also collect and utilize informant-based information. Rougemont-Buecking et al.36
in a large well-designed study showed fair to good agreement between a family member and direct interview for panic disorder and obsessive compulsive disorder, whereas poor agreement was seen with overall anxiety disorder and generalized anxiety disorder.36
Mendlewicz et al.37
reported an agreement kappa of 0.5 to identify affective disorders between a direct psychiatric interview and probands recollection.37
Gershon and Guroff38
reported kappa's for bipolar disorder 1=0.63, major depression=0.42, whereas for bipolar disorder 2 and schizoaffective disorder the kappa=0.38
One possibility that our values showed greater agreement than the genetic studies is that all of our subjects were long-term psychiatric patients with family that were knowledgeable of their medical history. In this report, we show that the MINI can also provide an accurate psychiatric diagnosis, and can be completed in a shorter amount of time in comparison with the SCID. This is important as it limits the intrusiveness of the NOK interview.
In this work, we attempted to simulate a typical NOK post-mortem interview with clinic patients and their NOK to see if the NOK were aware of the severity of psychiatric symptoms and mood state in the subjects. The ICC of all the scales ranged from 0.66 to 0.44 with the exception of the BISS depression subscale (0.28) and Barratt Impulsiveness Scale (0.36). Using Landi and Koch39
interpretation of the similar kappa, these scores showed at least a ‘moderate' level of agreement. Although Barratt Impulsiveness Score had a poor level of agreement by ICC, the mean scores were found to be statistically equivalent.
This study gathered retrospective information obtained by an informant. The reliability of this type of data has several areas of potential confounds. Most NOK under report symptoms and when interpreting the results, care must be given to who the informant is. For example, parents may not be aware of their children's alcohol/drug use nor of their sexual drive and many spouses may not have detailed history of the other spouse's childhood abuse. This study uses a small sample size of non-randomly selected subjects; even so, our results are similar to other reports using a variety of instruments.34, 35, 40
Because our focus was on mood disorders not all DSM axis 1 diagnoses were encountered and we were unable to report positive agreement data for the diagnoses of: obsessive compulsive disorder, post-traumatic stress disorder, schizophrenia and adult attention deficit hyperactivity disorder. Additional work is needed to study the concordance of these disorders and understand how long after death a NOK can provide reliable mood symptom ratings.
Overall, we show in a group with severe mental illness that an informant interview of the NOK can provide useful information, which can be used to better analyze post-mortem biological information. There are significant caveats to reliable post-mortem data collection: (1) the interviewer must have extensive experience conducting clinical interviews, (2) the informant must have regular contact with the subject, (3) multiple informant interviews should be conducted if available and (4) the psychometric instruments used must be geared toward clinically obvious symptom levels.