CG144 provides, as expected, a comprehensive review of the relevant literature with, in general, correspondingly useful practical clinical guidance on this topic. There are two specific aspects, however, which puzzle me.

1. No empirical evidence is adduced by the guideline development group (GDG) to support changing to 'scanning within 4 hours' from the current practice of starting LMWH immediately and then scanning when next feasible (often only in usual working hours) for a patient with suspected VTE.

On pages 83-84 it is explicitly stated:
'A single dose of parenteral anticoagulant is likely to have an overall benefit to patients who are waiting for diagnostic imaging to exclude a PE', and 'The GDG decided to recommend anticoagulation if diagnosis of PE cannot be confirmed immediately based on safety reasons; no economic evidence was considered to inform this recommendation.'

On p87 it says 'There was no clinical evidence review regarding the use of anticoagulants while waiting for imaging in patients with “likely” probability of PE.'

The GDG state [p85] 'putting patients on LMWH is expensive and may expose them to unnecessary side effects.' This statement is unhelpful as they adduce no evidence to quantify these assertions, or to assess the magnitude of cost in reorganising on call arrangements for ultrasound scanning.

Without such quantitative data, how can one decide whether it is worth the major rearrangement necessary - especially in a time of austerity when cash-strapped trusts are being asked to reduce costs?

2. The recommendations for investigation for cancer in patients with apparently idiopathic VTE is based on one trial of 201 patients (out of 1020 patients referred) which had serious limitations and imprecision (as noted in the guideline - Table 73, p 194). No mention is made of the morbidity associated with false positive diagnoses here, so this evidence cannot be regarded as definitive. By contrast, in the section on thrombophilia testing in first-degree relatives (p212) it says 'There is a psychological impact associated with thrombophilia testing that could lead to stress and anxiety in patients.' Why does this same factor not apply equally to the former group?
In this light, it is particularly interesting that recommendation 10 (p88) states ‘Detection of other abnormalities in the chest area (the expert adviser to the GDG pointed out that CTPA may have an advantage in patients who are more than 50 years of age, who are also at an increased risk of cancer and more likely to have other abnormalities)’ yet on p199 we find ‘thorax CT, …[is] not cost-effective as the small increase in the number of cases detected does not justify the high rate of false positive cases’.

Perhaps it is premature to recommend major changes in practice where the empirical evidence is partial and there will be a massive impact on practice? Sadly, public expectation has now been raised by the media presentation of these guidelines, which has focused in particular on these two aspects.

Competing interests: None declared