An Overblown Critique of CMS OP-15

OP-15 for imaging effectiveness in atraumatic headache is coming, vigorously opposed by many.  To date, most of the opposition has been in principle, or with specific clinical concerns.

This is a different approach to the problem – looking at whether the patients that CMS identified as “inappropriate” were actually appropriate exceptions.  This was a retrospective chart review of 748 charts that were referred back to 21 hospitals as “inappropriate” following a “dry run” of OP-15.  Based on individual chart review, the authors found documentation of one of the exclusion criteria in 489 of them – 479 based on the clinical criteria, and 35 based on administrative criteria (some met both).  They then look at those 259 patients for whom there is no CMS exception for their CT, and they claim that 136 of those were clinically warranted.  They therefore conclude that only 125 of the original 748 were accurately identified by this quality measure as inappropriate use of CT in atraumatic headache, and that this measure is garbage.

And, a quick Google News search finds an extensive parade of indignant headlines pulled from ACEP’s press release, condemning the measure.

But, this study misses the point.  It’s not CMS’ responsibility to comb through individual charts to find these exclusion criteria.  The onus is on clinicians and hospitals to ensure their documentation clearly expresses the indications for CT in those cases that meet the exclusion criteria, and the purpose of this dry run is to help hospitals identify where the information they are supplying to CMS is deficient.

Then, I expect CMS to take a low opinion of the additional patients in whom these authors felt the imaging was clinically warranted.  Of the 78 patients for whom the authors felt ACEP guidelines for imaging were met, 73 of them met only the Level C recommendation: >50 years of age with a new type of headache and a normal neurologic examination.  Then, there is another set of patients with headaches on warfarin, who had recent neurosurgery, or had known hydrocephalus that they claim are misclassified by CMS – but I can’t see how the misclassification isn’t on the documentation end, as headaches in all those patients should meet ICD-9 339.44 “Other complicated headache syndrome,” which is an exclusion to the rule as well.

So, even just on first pass, I’m not sure this is an effective tool with which to influence revision of OP-15.  I expect this measure to go into effect as planned – and it will be up to us to document appropriately and thoroughly, and then to monitor and demonstrate that compliance results in measurable patient harms.

“Assessment of Medicare’s Imaging Efficiency Measure for Emergency Department Patients With Atraumatic Headache”
http://www.annemergmed.com/webfiles/images/journals/ymem/FA-JDSchuur.pdf

Further Harms of IV Contrast

Radiation: cancer.  Iodinated contrast: renal injury.  Now, iodinated contrast: thyroid dysfunction.

This is a retrospective, matched, case-control study performed in Boston to evaluate any association between CT administration of IV contrast and hyper- and hypothyroidism.  They gathered 178 new-onset hyperthyroid and 213 new-onset hypothyroid cases and statistically matched them in their patient database to euthyroid “controls”.  There were no significant differences between the groups at baseline – although, they don’t match between terribly many clinical variables.

In the end, they find the patients who developed thyroid dysfunction had higher rates of iodinated contrast exposure – primarily from cardiac catheterization, but also from CT scans.  For hyperthyroidism, 6.1% of controls had contrast exposure, whereas 10.7% of their hyperthyroid patients had received contrast.  For hypothyroidism, the numbers are 8.5% controls vs. 12.2% hypothyroid.

It’s a bit of a backwards way to approach it – ideally they’d compare a group receiving iodinated contrast against a group that did not, and observe the incidence of thyroid dysfunction – but it seems that’s not the format of data to which they have access.  In any event, the physiologic basis is reasonable for the association – more data needed to confirm these findings.

Just in case you needed another reason to not order a contrasted CT.

“Association Between Iodinated Contrast Media Exposure and Incident Hyperthyroidism and Hypothyroidism”
http://www.ncbi.nlm.nih.gov/pubmed/22271121

False-Negative Abdominal CTs

This is an article from the radiology literature that essentially tries to say that CT is not the imaging modality of choice for upper abdominal pain.

It’s a retrospective review of 235 patients over a four-year period who had CTs of the abdomen reported as “normal” or “non-diagnostic” in the setting of upper abdominal pain.  They determine false-negative studies if another diagnostic modality eventually provided a definitive diagnosis for the patient’s symptoms.  Out of the 235, 81 were lost to follow-up and 27 were excluded for other reasons.  Of the remaining 127, 46 were classified as false-negative and 81 were classified as true-negative.

The misses?  23 cases of pancreaticobiliary disease (biliary colic, cholecystitis, choledocholithiasis), 12 cases of gastritis/gastric ulcer disease, and 6 miscellaneous cases that included Mediterranean fever and prosthetic valve endocarditis.

So, yes, there is some inkling that CT of the upper abdomen is going to miss a segment of pathology.  On the other hand, this paper presents incomplete data regarding the true positives and false positives – making evaluation of this specific imaging indication incomplete other than to remind clinicians that the evaluation may need to continue in the setting of a negative CT.

“Negative predictive value of intravenous contrast-enhanced CT of the abdomen for patients presenting to the emergency department with undifferentiated upper abdominal pain”
www.ncbi.nlm.nih.gov/pubmed/22072086

Novel Ischemia Prediction from CCTA

One of the arguments against CCTA is that it only describes coronary anatomy – and has no demonstrated clinical predictive value regarding whether the observed lesions are flow-limiting or potentially related to anginal symptoms.  This study develops a computational fluid dynamics model that attempts to predict flow through coronary stenoses seen on CCTA.

Korea, Latvia, and California come together to evaluate 103 patients in a multicenter trial in which patients with suspected CAD underwent CCTA, invasive coronary angiography, and fractional flow reserve measurement.  They used only 256 and 64-slice scanners for CCTA, and CAD was quantified as none, mild (0-49%), moderate (50-70%), and severe (>70%).  Patients then underwent invasive coronary angiography where ischemia-related flow-limitation was defined as a fractional flow reserve of < 0.80.  The study group then developed a method of deriving the FFR from CCTA data, and compared it to the actual measurements from invasive coronary angiography using the same threshold value.

The conclusions from this article depend what takeaways you’re looking for.  On one hand, the FFR-CT method was pretty decent – 87.9% sensitive and 82.2% specific regarding their definition of ischemia-causing lesions.  The other real takeaway is that CCTA has abysmal performance at the threshold typically used in the CCTA studies of >50% stenosis.  Their calculated +LR for CCTA stenoses >50% was only 1.51 in the setting of a specificity of 39.6%.  To me, another nail in the coffin showing CCTA is the d-Dimer of CAD, leading to a ton of unnecessary testing.

Considering it took them 5(!) hours to generate the FFR-CT measurement based on Newtonian fluid and Navier-Stokes equations on a parallel supercomputer, I don’t think we’ll be seeing this anytime soon – but hope is out there for the future.

“Cardiac Imaging Diagnosis of Ischemia-Causing Coronary Stenoses by Noninvasive Fractional Flow Reserve Computed From Coronary Computed Tomographic Angiograms”
http://www.theheart.org/article/1299631.do

Do/Don’t Scan the Trauma Patient

In a study attempting to build consensus, they discovered philosophical differences between the trauma team and the emergency physician.

This is a prospective observational study in which 701 blunt trauma activations at LAC-USC were enrolled, with the EP and the trauma team each giving an opinion on which CT studies were necessary.  The authors then reviewed which scans were obtained, sorted out the scans that were undesired by one or both physicians, and determined whether any injuries would be missed.

Bafflingly, 7% of the 2,804 scans obtained during the study period were deemed unnecessary by both the emergency physician and the trauma attending – yet were still performed.  The remaining 794 undesired scans were desired by the trauma team but not the emergency physician.  Their question – would anything of significance been missed if the scans had been more selectively ordered?

The answer is – yes and no.  The trauma surgeon authors state yes, and justify that by saying that many of the abnormalities missed on CT required closer monitoring – just because none of the missed injuries deteriorated during the study period does not mean they were not significant.  The emergency physician authors point to a 56% reduction in pan-scanning, the benefits of radiation and cost reductions, and hang their hats on the fact that none of the hypothetically missed injuries changed management.

So, who is right?  Both, and neither, of course.  Emergency physicians and trauma teams should work on developing evidence-based clinical decision rules to support selective scanning in blunt trauma – and then try this study again to see if they can generate results they can agree on.

Definitely a fun read.

As far as medical literature goes, of course.

“Selective Use of Computed Tomography Compared With Routine Whole Body Imaging in Patients With Blunt Trauma.”
www.ncbi.nlm.nih.gov/pubmed/21890237

C-Collars Cannot Stabilize Unstable Injuries

This is another cautionary anatomic study that demonstrates cervical collars are not adequate immobilization devices – except in patients who already do not need them.

This is a cadaveric spinal immobilization study in which C5/C6 instability was induced, and the Ambu extrication collar, the Aspen collar, and no collar were evaluated for range of bending and rotation during a bed transfer simulation.

The results are pretty straightforward.  Before the instability was induced, patients had minimal neck movement, whether immobilized or not.  After instability was induced, the patients all had significant bending and rotation – nearly the same for the patients in the collars as in no collar at all.

This is consistent with the small amount of prior work done in actual unstable spines; most of the cervical collar data is in healthy volunteers.  The limitations of a cervical collar should be recognized, and patients should have their cervical spine evaluated and cleared or intervened on immediately.

“Cervical collars are insufficient for immobilizing an unstable cervical spine injury.”
www.ncbi.nlm.nih.gov/pubmed/21397431

MRI After Negative CT in Obtunded Trauma

In contrast to the recently reviewed study showing 5 surgical injuries in 174 patients complaining of neck pain after a negative CT c-spine, this study of MRI in obtunded trauma patients with a negative CT c-spine showed no surgical injuries.

Specifically, this is a retrospective review from U.C. Davis in which they looked at 512 patients who underwent both CT c-spine and MRI c-spine.  They found 150 patients who were confused/obtunded, had otherwise normal neurologic examination, and had a negative initial CT c-spine.  Half of these patients had an injury identified on their MRI, but none of them were unstable ligamentous injuries or structural abnormalities requiring surgical intervention.

This is more relevant to our trauma colleagues who need to mobilize people in the ICU to prevent other complications, and external validity is limited in a single-center study, but it’s a mark on the side of keeping the standard of care at CT and not proceeding to MRI in an irrational manner.

“The Value of Cervical Magnetic Resonance Imaging in the Evaluation of the Obtunded or Comatose Patient With Cervical Trauma, No Other Abnormal Neurologic Findings, and a Normal Cervical Computed Tomography.”
www.ncbi.nlm.nih.gov/pubmed/21857257

When Does a Repeat Head CT Have Value?

Not practice-changing, but an interesting observational report regarding when these authors found value in performing a repeat head CT after minor head trauma.

Specifically, they looked at a subgroup of patients whose initial head CT was normal after blunt trauma, but received a repeat head CT an average of ~8 hours later for an abnormal neurologic examination.  These abnormal neurologic examinations were further stratified into three groups – a “persistently abnormal” exam, a “acute deterioration” in neurologic examination, and a catchall “unknown” group.  The first two groups had mean GCS of 12.4 and 14.5 – but the reason why the “unknown” group is what it is – their average GCS is 4.

They found that repeating the head CT in the 61 patients they had with persistently abnormal neurologic examinations did lead to some worsening of the initial findings – but did not change management in any cases.  However, 6 of the 21 patients who had an acute deterioration had a change in management, as well as 1 patient in the unknown group.

Small sample, but interesting, nonetheless.

“Utility of Repeat Head Computed Tomography in Patients With an Abnormal Neurologic Examination After Minimal Head Injury.”
www.ncbi.nlm.nih.gov/pubmed/21857258

When Is Blunt Chest Trauma Low-Risk?

According to this study, always – but rarely.

This is a prospective 3-center trauma study attempting to discern clinical variables that predicted the absence of serious traumatic chest injury in the setting of blunt trauma.  2,628 subjects enrolled, with 271 of them diagnosed with a serious injury – pneumothorax, hemothorax, great vessel injury, multiple rib fractures, sternal fracture, pulmonary contusion, and diaphragmatic rupture.  They do a recursive partitioning analysis and identify a combination of seven clinical findings that had a 99.3% (97.4 – 99.8) sensitivity for serious traumatic injuries.

But, I might be missing the point of this instrument a little bit.  Only 10% of their cohort had a traumatic injury – yet out of the remaining 90% without serious traumatic injury, their rule could only carve out 14% as low risk.  These low risk patients, the authors then propose, obviates any chest imaging at all.  While I am all for reducing unnecessary testing, this seems like an awfully low yield decision rule.  Yes, this study identifies young patients who are perfectly fine after a low-risk blunt trauma and do not need even an x-ray – but I’d really rather see more work preventing some of the 584 chest CTs performed in this cohort.  Additionally, their criterion standard for negative imaging is inadequate – most received CXR alone and there’s no follow-up protocol to test for possible missed injuries, whether clinically significant or not.

Considering the criteria they identified, it seems they could almost get equal or greater reduction in imaging if the clinicians were simply a little more thoughtful with respect to knee-jerk imaging in trauma.

“Derivation of a Decision Instrument for Selective Chest Radiography in Blunt Trauma.”
www.ncbi.nlm.nih.gov/pubmed/21045745

Forced Diuresis Prevents CIN

I admit, I was shocked when I got to the end of the paper and found the authors had no disclosures – it seems nearly every study concerning a commercial product has someone on the payroll.  Heck, the study is even registered with clinicaltrials.gov, and they didn’t change their protocol at all.

Anyway, this paper is in regards to the RenalGuard system, which is basically a closed-loop system that replaces a furosemide forced diuresis with normal saline.  They compare this to “usual therapy”, which, for them, is sodium bicarbonate and n-acetylcysteine (NAC) for the prevention of contrast-induced nephropathy as a result of some iodixanol contrast load.  Basically, they ran this system through a few patients who were at high-risk for CIN for ~5 hours around the time of their contrast procedure and tried to get their urine flow rate >300 mL/hr.  When successful, those patients had significantly less CIN than the “usual therapy” group (10% vs. 20%).

So, seems like it works.  There was more pulmonary edema (3 vs. 1) in the RenalGuard system, and more electrolyte abnormalities to replace, but this is a therapy that might yet have some utility.  It may even be practical in an ED setting, to a limited extent.

“Renal Insufficiency After Contrast Media Administration Trial II (REMEDIAL II)”
www.ncbi.nlm.nih.gov/pubmed/21518686