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- ABPA, allergic bronchopulmonary aspergillosis
- AST, aspartate transaminase
- CF, cystic fibrosis
- CFRD, cystic fibrosis related diabetes
- ESR, erythrocyte sedimentation rate
- γGT, γ gluteryltransferase
- RAST, radioallergosorbent test
Some years ago, when I was an SHO, I questioned a consultant about the reasons for requesting a routine chest x ray on a patient who was clinically well. I was told that it was important to “keep one step ahead of the patient”. That response satisfied me at the time, and I have used the quote from time to time when explaining to parents the reasons for undertaking investigations in children who have no overt clinical problems. Nowadays, clinicians and families are likely to require more tangible evidence of benefit before agreeing to children undergoing detailed investigations, particularly if these may be uncomfortable or distressing. Jaffe et al's retrospective review is therefore a welcome attempt to address this issue with respect to routine annual blood tests in young children with cystic fibrosis (CF).
Annual review of patients with CF has been practised for some time in most CF centres in the UK and is now recommended by national guidelines.1 The aims of annual review are numerous, but include the need to screen for asymptomatic disease outside the respiratory system. Most of these screening investigations require blood tests. As much of the treatment recommended for children with CF is directed towards preventing clinical deterioration and improving long term outcomes and survival, the notion of being able to detect complications at an early, subclinical stage is one which fits well with the whole ethos of clinical management.
One of the difficulties in assessing this paper is that, in clinical practice, each screening blood test result is not considered in isolation when the annual review is discussed with parents and appropriate action is considered. An example of this is the early detection of CF-related liver disease, where there is no satisfactory screening test and by the time the disease can be diagnosed with certainty, there is often irreversible cirrhosis. In assessing whether any changes were significant, one would consider not only the results of liver function tests, but also clinical findings of enlarged liver or spleen and liver ultrasound appearances.
A second difficulty is that a single measure provides limited information which may not trigger a change in management and results are always considered in the context of previous ones. For example, it is recommended by some that biochemical liver disease should only be considered to be present if liver function tests were abnormal on two consecutive annual reviews.2 In a child with borderline iron deficiency anaemia one would be more inclined to treat with iron if these findings persisted despite dietary advice.
The benefits of obtaining information from blood tests are much broader than those considered in this study. First of all, in the UK and other countries, national CF databases are now collecting data prospectively about incidence and prevalence of complications of CF, such as liver disease and nutritional status. Analysis of longitudinal data from such large databases will provide important information about risk factors, prognosis, and possible strategies for prevention.3 Without information from blood tests, such data will be incomplete.
Secondly, Jaffe et al have assessed changes in management, but there are other important outcomes from annual review. It provides everyone with an opportunity to discuss the child and his/her progress in detail and is regarded by most families as a useful and rewarding exercise. Parents, who are generally as well informed as their doctors, are often very gratified to hear about a normal result. This is particularly the case in a recently diagnosed child, where it is important to assess whether previously abnormal results have improved. While I agree with Jaffe et al's recommendations, I feel that the most compelling reasons for having a complete dataset of information in young children at annual review were not evaluated in this study.