Use of ICD-10 diagnoses in Danish psychiatric hospital-based services in 2001-2007

Abstract

The Danish version of the ICD-10 chapter on mental and behavioural disorders has 380 different diagnoses when three digits are used. This study examines how many of the available diagnoses were used and to what extent in Danish psychiatric hospital-based services in the period from 2001 to 2007, through an analysis of the total number of diagnoses reported to the Danish Psychiatric Central Research Register (n=1,260,097). The 50th percentile (50.1%) was reached by using 16 diagnoses (4.2% of 380 available). The three most frequently registered diagnoses were paranoid schizophrenia, alcohol dependence and adjustment disorder, used 10.2%, 8.3% and 5.9% of the times, respectively. Seven diagnoses (1.8%) were used between 1 and 4 times during the 7-year period. One hundred nine (28.7% of available diagnoses) were used less than 100 times each. These data suggest that it may be sensible to reconsider the number of diagnoses needed in the revision of the ICD-10 chapter on mental and behavioural disorders.

Psychiatric health care statistics and epidemiological research almost always use a very limited number of classificatory groups for result presentation, rarely more than 8 to 10. Current classification systems, the ICD-10 and DSM-IV-TR, open up for several possibilities for detailed diagnosing aiming at treatment and research. The ICD-10 chapter on mental and behavioural disorders, used in Denmark since January 1994, has 380 different diagnoses when three digits are used (xx.x). The purpose of this study was to investigate how many of the psychiatric diagnoses available were used and to what extent in the Danish psychiatric hospital-based services in the period from 2001 to 2007.

The data used were all diagnoses reported to the Danish Psychiatric Central Research Register (DPCRR) 1 from January 1, 2001 through December 31, 2007. Diagnoses are reported to the register in connection with discharge from a treatment episode. Diagnoses from inpatient and outpatient treatment episodes as well as visits to psychiatric emergency services were included. Patients in community psychiatric treatment were included in the group of outpatients. Both main and auxiliary diagnoses were considered.

During the seven-year period, 1,260,097 diagnoses from 1,041,589 discharges of 653,754 patients from in- and outpatient treatment episodes were reported to the DPCRR. All 380 possible diagnoses from the Danish version of the ICD-10 were used.

The 50th percentile (50.1%) of the total of 1,260,097 diagnoses was reached by including 16 different diagnoses, with F20.0 (paranoid schizophrenia) as the most frequently used, 128,537 (10.2%) times. F10.2 (alcohol dependence syndrome) was used 104,445 (8.3%) times, and F43.2 (adjustment disorder) 74,687 (5.9%) times.

The 75th percentile was reached by including 49 diagnoses (Figure 1). One hundred and forty-six diagnoses (38.4%) were sufficient to reach the 95th percentile. One hundred forty-four diagnoses (37.9%) were registered less than 200 times each; 109 (28.7%) less than 100 times each; 141 (37.1%) were used 0.01% or less of the total of 1,260,097 diagnoses.

Three diagnoses were used only twice: cluttering (F98.6), abuse of volatile solvents (F18.8), and amnestic syndrome due to abuse of volatile solvents (F18.6). Two were used only 3 times: acquired aphasia with epilepsy (F80.3), and other impairment of behaviour due to profound mental retardation (F73.8). Two were used only 4 times: pica of infancy and childhood (F98.3), and other mental and behavioural disorders due to use of hallucinogens (F16.8).

These results indicate that very few of the 380 available diagnoses in the Danish version of the ICD-10 account for a majority of the diagnoses given. This is in line with the report by Müssigbrodt et al 2, who investigated 25,470 main diagnoses given in 19 departments from 10 countries in 4 continents. They found that 10 diagnoses accounted for 40% of all cases and 121 were used in less than 0.1% of the cases.

In the absence of a clear knowledge about the pathogenesis of mental disorders, psychiatry is open to introducing new diagnostic concepts. This process is welcomed by the pharmaceutical industry 3, and may be supported by the decreasing threshold for discomfort and personal responsibility for one’s own life in Western populations 4.

This tendency could be corrected when revising the ICD and DSM systems, preferably by involving also the WPA 5, and by rethinking the evidence needed for coining new “disorders”, although taking cultural diversities 6 into account.

As our study was based on a register covering hospital- and community-based psychiatric practice, we cannot exclude a possible usefulness in private practice of some of the diagnoses not frequently used in public settings.

Figure 1 The 49 ICD-10 categories accounting for 75% of the diagnoses given in Danish public psychiatry from 2001 to 2007

Figure 1.