5th April 2013: Prospective Pilot Derivation of a Decision Tool for Children at Low Risk for Testicular Torsion

050413

Where can I find this paper?

http://www.ncbi.nlm.nih.gov/pubmed/23517259

What is this paper about (what is the research question)?

Is it possible to exclude a diagnosis of testicular torsion on the basis of history and examination alone?

Summary of the Paper

Design: prospective cohort study for derivation of a clinical decision rule

Objective: to derive a pilot clinical decision tool with 100% NPV for testicular torsion

Outcome: Proposed low-risk decision tree determined by recursive partitioning based on historical and examination variables recorded prior to ultrasonographic or specialist assessment

Reference Standard: presence of testicular torsion defined by: diminished blood flow on testicular doppler US (read by paediatric radiologist), or ischaemic/infarcted testicle at operative assessment (by paediatric surgeon or urologist), or presence of testicular atrophy at 1- to 3-month follow-up (contralateral difference in testicular size as measured by orchidometer)

Participants: Convenience sample of male patients aged 0-21 years with acute (<72h) testicular pain presenting to a tertiary children’s ED between July 2005-February 2008

Results: 228 patients (of 552 eligible patients) were enrolled. 55 (10% of eligible patients) were diagnosed with testicular torsion, of whom 21 (9.2%) were among those recruited into the study.

Odds ratios:

  • Horizontal/inguinal testicular lie OR=18.17 (95%CI 6.2-53.2)
  • Unilaterally or bilaterally absent cremasteric reflect OR=11.01 (95%CI 3.14-38.64)
  • Nausea or vomiting OR=5.63 (95%CI 2.08-15.22)
  • Age 11-21 years OR=3.9 (95%CI 1.27-11.97)
  • Scrotal oedema OR=3.42 (95%CI 1.21-9.69)

Authors’ Conclusions:

Patients with normal testicular lie, without nausea or vomiting, and between the ages of 0-10 years are at low risk for having testicular torsion despite the presence of acute testicular pain. Thus, patients who do not meet all three of these criteria should be considered at risk for possible testicular torsion and should undergo subsequent emergent evaluation.

On the study design

The inclusion and exclusion criteria seem sensible too; patients were included in the age 0-21 group with testicular pain of <72h duration, and subsequently excluded if they had prior ipsilateral inguinal or  urological surgery, definite hydrocoele or inguinal hernia or known diagnosis at initial evaluation. The authors have tried to maximise their awareness of the patient population by using database searches during the study period to identify “missed” participants.

Unfortunately the convenience sample meant that more than half of patients presenting during the study period who were diagnosed with testicular torsion were not included in the data collection. This means the study was underpowered for the question it intended to ask. Convenience sampling is often significantly cheaper and easier than a 24-hr recruiting presence in the ED but as this paper demonstrates it can have a profound effect on the numbers recruited, particularly in conditions which are relatively rare.

Various measures have been utilised to minimise the effect of bias; standardised data collection forms are always helpful in this regard. The initial ED assessments were made prior to ultrasound or speciality assessment which acts as a blind assessment, although surgeons and radiologists determining the outcome were not blinded. The authors argue that clinical information is essential in patient care, but many studies use blinded radiological assessment after the event and this could certainly have been undertaken in this case even if the surgeons could not be blinded.

In the UK, it is likely that testicular tissue would be sent for histological diagnosis; arguably, this is a more definitive outcome and could certainly be blinded.

The decision to follow-up at 1- 3 months with orchidometer measurements when baseline measurements were not taken is an odd one; surely this invites all manner of confounders? Thankfully this did not actually involve any subjects but it seems a strange choice – perhaps an afterthought?

What were the results and what does this mean?

Odds ratios for the various examination and historical findings were given in table 2. These variables were formulated into a decision rule using recursive partitioning.

050413 Table 2

The most strongly predictive finding was abnormal testicular lie, with an odds ratio of 18.17 but a very wide confidence interval (95%CI 6.2-53.2) reflecting the small study numbers.

The decision rule in itself had the following test characteristics:

  • NPV 100% (95%CI 98-100%)
  • Sensitivity 100% (95%CI 98-100%)
  • Specificity 44% (95%CI 38-50%)
  • PPV 15% (95%CI 11-21%)

Obviously an NPV of 100% and sensitivity of 100% is impressive and important in a rule-out tool such as this, but the specificity and positive predictive value are very low. This would ordinarily expose a large number of patients to further examination and assessment, but as these patients have not yet had doppler examination it may not be unworkable.

However, this rather raises the question – if I saw a 7-year-old patient with testicular pain and vomiting, would I really need this decision rule to tell me that he needed further assessment to exclude testicular torsion?

What can we take from this paper into clinical practice?

I don’t think that at this stage we can rely fully on the absence of abnormal lie, nausea/vomiting and age <10 years to exclude testicular torsion as a diagnosis in patients with acute testicular pain in the ED, but it will be interesting to see how the proposed decision tool performs in external validation.

However, taking a step back, we are able to see that what this paper is  trying to do is formalise the process of diagnostic suspicion of testicular torsion. We have little information about the skill and experience levels of the ED physicians performing the initial assessment. Does this paper tell us anything we don’t already know as clinicians?

Well, maybe yes – it looks as though we can be a little reassured by the group of patients aged <10 without abnormal lie or nausea/vomiting. The use of sensitivity analysis adds to this – the authors have included  patients lost to follow-up and assumed that they had torsion, finding that the decision rule performed just as well.

However, we really need to see how the rule performs in a fresh setting when applied to all patients rather than a convenience sample.

More questions to ask

  • How would this rule perform in a different setting – an external ED or even in general practice?
  • Does this decision process reduce our referrals for expert assessment/doppler US or does the low specificity/PPV represent a potential increase in referral, time and cost?

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