Non-alcoholic fatty liver disease
BMJ 2014; 349 doi: https://doi.org/10.1136/bmj.g4596 (Published 29 July 2014) Cite this as: BMJ 2014;349:g4596
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Sir, we read this interesting paper on the complex subject of NAFLD by Sattar, Forrest and Preiss. Unfortunately their clinical algorithm contains several important errors we would like to elucidate :-
1. The contents of the two Statement boxes at the start of the Algorithm seem arbitrary. What about the inclusion of choices for all the logical combinations of variables such as “symptomatic / asymptomatic”, “fatty liver on US / no fatty liver on US” and “normal / abnormal LFTs”?
2. The right-hand rectangular box displaying the text “if AST:ALT > 0.8, consider specialist referral” contains a decision ( resulting from a question ) followed by a process. These different flow chart components cannot be included in the same box and need separating ( q.v. re-designed algorithm below ). Decisions should be displayed in diamond-shaped boxes and processes in rectangular-shaped boxes according to the BSI ( British Standards Institute ) Standard BS4058 for flow charts [ 1, 2 ].
3. The algorithm will fail if the patient’s AST:ALT ratio is equal to 0.8 because the algorithm has no selectable choice for this value.
4. The algorithm uses the numeric pointers “1”, “2” and “3” and a large amount of text to transfer control from the bottom of the algorithm to the middle of it. A clinical algorithm in the form of a flow chart is ideally suited to displaying cyclical data flow using arrow-headed, data-flow lines without the need for descriptive text or pointers. Pointers used in this context are analogous to the use of the GOTO statement in the computer language, BASIC, which encourages “unstructured” programming.
We understand that designing a complex cyclical algorithm like this one is a difficult job but we feel that our re-designed version shown below clarifies the decision-making logic and data flow using “direct wiring” to replace the repetitive text describing the cyclical data flow within it. The re-designed algorithm also disambiguates the display of the three types of results from the patients’ clinical reviews for each of the three levels of ALT enzyme abnormality into “Better”, “Static” and “Worse” and the different clinical interventions that need to be followed.
References
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Management of Pneumothorax. Clinical algorithms should be standardised.
British Medical Journal, 307, 443, 1993.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1678411/
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2. Colman A, Athey R, Richards B.
Flawed logic, duplicate and missing data make the opioid algorithm in Figure 2 unusable.
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Competing interests: No competing interests
The article fails to mention the main causes and most effective treatments for NALFD. This is not surprised because, although well researched, these causes and treatments are not well known. Consumption of vegetable oil, containing omega-6 fatty acids such as linoleic acid, is the most effective way of inducing fatty liver disease [1]. Saturated fats reverse NAFLD and beef fat does this most effectively [2]. Sugar, particularly fructose, also causes NAFLD. Omega-3 fats and medium chain triglycerides are beneficial.
Omega-6 is an essential fatty acid. We need to consume 0.5% of total calories as omega-6. The problem is that in the West we have 10%, which is twenty times as much as is good for [3]. Vegetable oil is widely used in cooking and food processing. Excess omega-6 fats are converted to inflammatory prostaglandins and liver inflammatory changes result. This pathway is inhibited by omega-3 fats. Ideally omega-3 and omega-6 intake should be equal but in the West omega-6 intake is twenty times greater [4]. Heating polyunsaturated omega-6 fats results in toxic oxidation products, which are far worse than the trans fats that vegetable oil has replaced [5], and these may cause further liver damage.
Olive oil is probably almost as bad. It contains 20% linoleic acid when pure and more when nut or vegetable oil is added. This practice is universal to cut the cost of olive oil production [6].
The inclusion of vegetable oil and the reduction of saturated fat continue to be seen as part of a healthy diet. We can therefore expect to see a continuing rise in the incidence of NAFLD.
References:
1. AHS13 Victoria Prince — Fatty Liver: Is It the Fat's Fault? http://www.ancestralhealth.org/post/ahs13-video-update
2. Beef fat prevents alcoholic liver disease in the rat, Alcohol Clin Exp Res. 1989 Feb;13(1):15-9
3. Fish, Omega-3 and Human Health by William Lands
4. Diets could prevent many diseases, William E. M. Lands, Lipids, April 2003, Volume 38, Issue 4, pp 317-321
5. The Big Fat Surprise by Nina Teicholz
6. Extra Virginity by Tom Mueller
Competing interests: No competing interests
Unselected screening for liver disease may not be cost-effective
Sattar and colleagues review the epidemiology, manifestations and management of of non-alcoholic fatty liver disease [1]. Their recommendations include the need to consider screening for other liver conditions such as chronic viral hepatitis, autoimmune liver disease, haemochromatosis, or drug induced liver injury. The value and cost implications of routine screening for rarer causes of liver disease in individuals with abnormal liver function tests is unclear.
Lilford and colleagues conducted a prospective study conducted in 11 primary care practices, enrolling 1290 individuals with abnormal liver function tests[2]. A diagnosis was established in less than 5% of cases. Only 17 (1.3%) of individuals were diagnosed with a condition requiring specific treatment, of which the majority (13) had viral hepatitis.
In a study by Armstrong and colleagues [3] of 1,118 patients seen in primary care, NAFLD and alcohol related liver disease were the commonest cause of abnormal liver function tests (26.4% and 25.3% respectively). Auto-immune and inherited metabolic conditions accounted for only 1% each.
We reviewed clinical notes, imaging and test results for three hundred and thirty eight consecutive patients investigated for with abnormal liver function tests, who presented to a large tertiary care hospital over a one-year period. We found alcoholic liver disease (22%) to be the commonest underlying diagnosis. A thorough history and ultrasound had the highest diagnostic yield, followed by testing for chronic viral hepatitis, which reached a diagnosis in 11% of patients. The cost per diagnosis varied substantially between tests (Table 1). The yield of screening for metabolic and auto-immune causes of liver disease was minimal.
Unselected diagnostic testing places a large financial burden on the NHS[4] often for limited diagnostic yield. Further prospective studies comparing different diagnostic strategies for patients with abnormal liver function tests are urgently needed in order to inform clinical practice.
1 Sattar N, Forrest E, Preiss D. Non-alcoholic fatty liver disease. BMJ 2014;347:g4596–g4596. doi:10.1136/bmj.g4596
2 Lilford RJ, Bentham L, Girling A, et al. Birmingham and Lambeth Liver Evaluation Testing Strategies (BALLETS): a prospective cohort study. Health Technol Assess Winch Engl 2013;17:i–xiv, 1–307. doi:10.3310/hta17280
3 Armstrong MJ, Houlihan DD, Bentham L, et al. Presence and severity of non-alcoholic fatty liver disease in a large prospective primary care cohort. J Hepatol 2012;56:234–40. doi:10.1016/j.jhep.2011.03.020
4 Marks M. Routine test batteries for cognitive impairment in older people may not be cost effective. BMJ 2011;343:d6330.
Competing interests: No competing interests