reliability and validity of ICD-10

Question 1

what is the ICD-10?

Answer 1

• includes both physical and mental health disorders
• originated from the 1893 international list of causes of death used to monitory global mortality and morbitity statistics
• in 1948, the WHO became involved and like the DSM, the ICD has seen many revisions over the years
• the current version, ICD-10, was published in 1982
• ICD-10 is used by clinicians and researchers, policy makers and client organisations around the world
• it provides a ‘common language’ so that data collected in different countries can be usefully compared

Question 2

mental health disorders and ICD-10 codes

Answer 2

• chapter 5 of the ICD-10 is entitled Mental and Behavioural disorders
• each diosorder has a code, starting with F
• the disorders are listed conseutively and there are 11 sections
• for example, schizphrenia, schizotypical and delusional disorders is one section grouped as F2–F29. F20 is the subcategory of schizophrenia and this is further differentiated so F20.0 is paranoid schizophrenia, F20.1 is Hebephrenic schizophrenia, F20.2 is catatonic schizophrenia etc.
• each section has a few ‘leftover’ codes, allowing new disorders to be added, without having to recode the other disorders
• for example, F46 has no entry and F48 is other nonpsychotic mental disorders
• the codes are used for indexing medical records, making it easy when conducting research to find examples of people with specific conditions
• the system attempts to be comprehensive enough to include all known conditions but also to avoid repetution or overlap

Question 3

making a diagnosis using the ICD-10

Answer 3

• ICD contains both physical and psychological disorders and both are coded in the same way
• the clinician selects key words from an interview with a client that relate to their symptoms - such as hallucinations, delusions, incoherent speech, lack of emotion
• the clincian can look up these symptoms in an alphabetical index or may go straight to an obvious section such as schizphrenia
• the clinician then uses other symptoms to locate a subcategory
• for a patient who a clinician suspects is schizophrenic, they may select F20 and then F20.2 based on presenting symptoms

Question 4

improvements to the ICD-10

Answer 4

• the presentation, communication and interpretation of symptoms is shaped by language and culture
• ‘culture bias’ means that clients in one culture could be givne a different diagnosis from clients in another culture, despite presenting very similar symptoms, because of different use of language or different cultural norms
• this has posed problems for the international research community which ICD serves and led to a rigorous research programme to review differences in diagnostic practice and differing use of diagnostic terminology across the world
• the result was that the ICD-10 is available in many different languages and in appropriate cultural forms
• this process also helped to reveal inconsistencies, ambiguities and overlaps between disorders, which were then removed from the ICD

Question 5

validity of diagnosis affected by comorbitity

Answer 5

the validity of diagnosis can be seriously impaired by issues of comorbidity and symptom overlap
comorbidity is when an individual has two or more distinct illnesses at the same time
For example, major depression and schizophrenia both involve very low levels of motivation. This creates problems of reliability anc auses the clinician to be unsure whether the low motivation is due to depression or schizophrenia, or both

Question 6

strength of ICD-10 in terms of reliability - improvement between the ICD-9 and the ICD-10

Answer 6

one strength of the ICD-10 is improvements in reliability
research evidence by Ponizovsky in 2006, from a large-scale longitudinal study found that PPV scores (the proportion of people who retain the same diagnosis when reassessed) increased by 26% for schizophrenia, 16% for mood disorders and 8% for anxiety disorders
therefore, this clearly shows improved reliability and suggests that the increased number of disorders from ICD-9 to ICD-10 has not detracted from the reliability of these diagnoses

Question 7

COUNTER ARGUMENT TO strength of ICD-10 in terms of reliability - improvement between teh ICD-9 and the ICD-10

Answer 7

however, Ponizovsky study did reveal some less satisfactory results for childhood disorders and personality disorders where PPVs were as low as 55% and 56% respectively
these PPVs may seem high in comparison with some of the figures quoted for the DSM but these figures are based on agreement at the category levles whereas the DSM figures are for more specific diagnosis
therefore, this suggests that the ICD may not be more reliable for specific diagnoses

Question 8

strength of ICD-10 in terms of reliability - inter-rater reliability

Answer 8

one strength of the ICD-10 in terms of reliabillity is that there is good consistency when two clinicians assess the same clients using the ICD-10
for example, Gian Galeazzi et al (2004) arranged for two researchers to conduct a joint interview to assess 100 consecutive clients for psychosomatic symptoms
the kappa values ranged from 0.69-0.97 showing very high levels of agreement between the clinicians
therefore, this level of agreement encourages confidence for using teh ICD-10 at least for some disorders

Question 9

strength of ICD-10 in terms of validity - good predicitve validity for schizophrenia

Answer 9

one strength of the ICD-10 in terms of validity is that Peter Mason et al (1997) has shown that the diagnosis of schizophrenia using the ICD-10 has good predicitve validity
the study compared different ways of making a diagnosis
the ICD-9 and ICD-10 were ‘reasonably good at predicting diability’ in 99 people with schizophrenia 13 years later, as measured by the global assessment of functioning questionairre
therefore, this shows that the initial diagnosis was useful and meaningful in terms of its ability to accurately predict future outcomes

Question 10

strength of ICD-10 in terms of validity - application to diagnosis

Answer 10

one strength of the ICD in terms of validity is its application to diagnosis
the WHO’s approach to the development of ICD-11 is that they aim to improve the ‘clinical utility of this sytem
the WHO has conducted a huge international survey of clinicians and found a preference for simplicity and flexibility, suggesting that the ICD-11 task force will be cautious about adding new disorders and are likely to merge disorders that are difficult to diagnose
therefore, this means that the system should become more ‘user-friendly’. hopefully by virtue of being easier to use, validity of diagnosis should also improve

Question 11

weakness of ICD-10 in terms of reliability - disclosure differences between clinicians

Answer 11

One issue with reliable diagnosis is that patients are often diagnosed using a clinical interview which can cause disagreement between clinical diagnosis because of a range of factors such as disclosure.
A patient could choose to disclose certain information to one clinician but in another interview may not disclose the same information and tell them different things to what they told the clinician in the first interview.
Therefore, this means that their diagnosis may not be accurate if the different clinicians are being provided with different information.

Question 12

weakness of ICD-10 in terms of validity - Rosenhan

Answer 12

one weakness ICD-10 is that the validity of a diagnosis can be questioned – this is supported by study evidence from Rosenhan 1973.
He found that patients who reported that they were hearing the word ‘thud’ were misdiagnosed as having schizophrenia and subsequently admitted to a psychiatric hospital.
The 8 pseudopatients in the original study were all diagnosed with schizophrenia despite the fact that they weren’t experiencing any actual symptoms. In a follow up study, he warned hospitals he would be sending in more pseudopatients, which resulted in a 21% detection rate despite no pseudopatients actually being sent in.
Therefore, this shows that there is difficulty in diagnosing patients accurately when they think that there are pseudopatients trying to get admitted.

Question 13

weakness of ICD-10 in terms of validity - comorbidity when diagnosing patients

Answer 13

In the diagnostic manuals, DSM, or ICD-10, which the clinicians use to diagnose patients in a clinical setting there is significant overlap in symptoms for different types of mental diseases.
This will make it difficult to accurately diagnose a patient who may have symptoms which could lie within a variety of mental disorders.
Individuals who have schizophrenia are likely to also have substance abuse related co-morbidities and individuals with depression are also likely to suffer from anxiety.
Therefore, this means that the chance of a patient receiving a valid diagnosis when their symptoms fall across a number of mental disorders in the diagnostic tool.
Furthermore, there is considerable overlap in symptoms in DSM. For example, disturbance of mood is found in both schizophrenia and depression making it more likely to misdiagnose an individual displaying these symptoms.