The figures given for the annual incidence of primary hypothyroidism
are for those cases picked up in diagnosis. Current protocol for
diagnosing hypothyroidism is suspect and therefore many cases of
hypothyroidism are not picked up in diagnosis.
The diagnosis and management of hypothyroidism is most certainly
problematical inasmuch that it is a highly controversial issue. This has
been the cause of much contention over the decades, none more so than
today. Clinical practice for (DMH) is seriously flawed. Misleading
information, with regard to the interpretation of the "reference interval"
plays a significant role in undetected hypothyroidism on a global scale.
For example, the biochemist will state on the laboratory report the word
“normal” this does not necessarily mean that the patient does not have a
thyroid condition. Professor Ralph Gräsbeck one of the developers of the
concept of the reference range, warned the medical profession in 1990 not
to use incorrect medical terminology such as the word “normal” when
referring to blood test results (1) and yet the writers of the article
insist on using this terminology. Maybe this is how the grey area has come
about with regard to GPs making diagnoses.
Also sole reliance on thyroid function test results plays a part. The
parameters for thyroid function tests are based on, “95% fiducial limits
of so-called healthy people” An assumed fixed basis of comparison of so-
called healthy people is very loosely termed. When there is such loose
terminology to set up the initial parameters for TFT results, then to
place sole reliance on the results is surely futile. There is too much
rigidity and not enough flexibility upon interpretation of thyroid
function test results. Whatever happened to all other indictors e.g.
signs, symptoms, clinical appraisal and patient history. The results of
blood tests were only ever meant to be used as one indicator only.
According to Professor Ralph Gräsbeck, “To make the diagnosis on the
basis of only one such test such as TSH only is decision-making based on
thin evidence”.
To quote Professor Ralph Gräsbeck again, “The main mistake made is to
consider values falling outside reference limits of healthy subjects (say,
122-172 g/L) as pathological (e.g. Haemoglobin 120 g/L is considered to
be anaemia). Such values may be only rare. Vice versa, values may be
pathological or associated with disease even though they are inside the
reference limits derived from a group of healthy people. (2/3)
The National Audit Office states that, “The development of clinical
guidelines on the appropriate treatment and care of people with specific
diseases and conditions within the NHS is the responsibility of the
National Institute for Health and Clincal Excellence. However, so far NICE
has not issued any guidance on the diagnosis and treatment of
hypothyroidism”.
The need for re-education in this area is of paramount importance to
both patients and the medical profession.
2. Grasbeck R: The evolution of the reference value concept. Clin
Chem
Lab Med 2004; 42(7):692-697.
3. Grasbeck R: Reference values and reference intervals. In McGraw-
Hill
Yearbook of Science & Technology 2008: pp 286-288. McGraw-Hill, New
York...London...2008.
Rapid Response:
Back to Basics
The figures given for the annual incidence of primary hypothyroidism
are for those cases picked up in diagnosis. Current protocol for
diagnosing hypothyroidism is suspect and therefore many cases of
hypothyroidism are not picked up in diagnosis.
The diagnosis and management of hypothyroidism is most certainly
problematical inasmuch that it is a highly controversial issue. This has
been the cause of much contention over the decades, none more so than
today. Clinical practice for (DMH) is seriously flawed. Misleading
information, with regard to the interpretation of the "reference interval"
plays a significant role in undetected hypothyroidism on a global scale.
For example, the biochemist will state on the laboratory report the word
“normal” this does not necessarily mean that the patient does not have a
thyroid condition. Professor Ralph Gräsbeck one of the developers of the
concept of the reference range, warned the medical profession in 1990 not
to use incorrect medical terminology such as the word “normal” when
referring to blood test results (1) and yet the writers of the article
insist on using this terminology. Maybe this is how the grey area has come
about with regard to GPs making diagnoses.
Also sole reliance on thyroid function test results plays a part. The
parameters for thyroid function tests are based on, “95% fiducial limits
of so-called healthy people” An assumed fixed basis of comparison of so-
called healthy people is very loosely termed. When there is such loose
terminology to set up the initial parameters for TFT results, then to
place sole reliance on the results is surely futile. There is too much
rigidity and not enough flexibility upon interpretation of thyroid
function test results. Whatever happened to all other indictors e.g.
signs, symptoms, clinical appraisal and patient history. The results of
blood tests were only ever meant to be used as one indicator only.
According to Professor Ralph Gräsbeck, “To make the diagnosis on the
basis of only one such test such as TSH only is decision-making based on
thin evidence”.
To quote Professor Ralph Gräsbeck again, “The main mistake made is to
consider values falling outside reference limits of healthy subjects (say,
122-172 g/L) as pathological (e.g. Haemoglobin 120 g/L is considered to
be anaemia). Such values may be only rare. Vice versa, values may be
pathological or associated with disease even though they are inside the
reference limits derived from a group of healthy people. (2/3)
The National Audit Office states that, “The development of clinical
guidelines on the appropriate treatment and care of people with specific
diseases and conditions within the NHS is the responsibility of the
National Institute for Health and Clincal Excellence. However, so far NICE
has not issued any guidance on the diagnosis and treatment of
hypothyroidism”.
The need for re-education in this area is of paramount importance to
both patients and the medical profession.
Diana Holmes
email:dianaholmes@tiscali.co.uk
References
1. Scand J Clin Lab Invest Supp 1990; 201:45-53
2. Grasbeck R: The evolution of the reference value concept. Clin
Chem
Lab Med 2004; 42(7):692-697.
3. Grasbeck R: Reference values and reference intervals. In McGraw-
Hill
Yearbook of Science & Technology 2008: pp 286-288. McGraw-Hill, New
York...London...2008.
Competing interests:
None declared
Competing interests: No competing interests