Month: August 2015

Gestational Age and D-Dimer Levels

In general, the utility of D-dimer for the evaluation of venous thromboembolism declines with gestational age.  The typical cut-offs for the 95th percentile, depending on your assay, become less and less relevant as pregnancy progresses.  Wouldn’t it be nice, perhaps, if we had reliable data?

So, well, here’s something:

One glaring hole in this data is the broad inclusion criteria of “healthy” women.  No testing was specifically performed to exclude asymptomatic venous thromboembolism, so the possibility exists of inclusion of small, subsegmental pulmonary emboli, or of non-occlusive lower extremity deep venous thrombosis.  The effect on this data would be to increase the 95% percentile, and to widen the 95th percentile confidence interval.

Jeff Kline has proposed gradually increasing cut-offs of 750, 1000, and 1250 ng/mL for the first, second, and third trimester, respectively (based on a standard cut-off of 500 ng/mL).  This sample is much larger than the one cited by Kline in his “PE in pregnancy” algorithm, but his appear to be reasonable, sensitive cut-offs.  By far, the most important aspect of evaluating pulmonary embolism in pregnancy is simply to communicate the uncertainty, and to inform and share decision-making with the patient along the way.

“Gestation-specific D-dimer reference ranges: a cross-sectional study”
http://www.ncbi.nlm.nih.gov/pubmed/24828148

The NNT of a Chest Pain Admission

To prevent death: 333.

In a bitterly complex analysis of Center for Medicare and Medicaid Services data, these authors describe a relationship between admission rate and subsequent cardiac adverse events.  Based on a statistical sample of Medicare patients visiting acute care hospitals, these authors calculate an admission rate for chest pain for each, and divide the sample into quintiles.  Then, the authors follow index visits for chest pain to those hospitals, and measure 30-day acute myocardial infarction or death.  Thus, a relationship between admission rate and poor outcomes.

The mean adjusted admission rate for chest pain ranged from 37.5% in the lowest quintile to 81.0% in the highest quintile.  Owing to the large sample size, many of the differences between hospitals in each quintile meet statistical significance.  However, the difference that leaps out at me the most, for-profit hospitals represented 24% of the highest quintile for admissions, while for-profit hospitals were only 7.8% of the lowest.

And, what was that massive variation and expenditure associated with, in terms of beneficial outcomes?  An inconsistent reduction in subsequent AMI and death which, through multivariate logistic regression, was equal to about 3.6 fewer AMIs and 2.8 fewer deaths per 1,000 patients – with very wide 95% CIs.

And, thus, to oversimplify and overstate the soundness of the analysis, the NNT of 333.

It seems very reasonable to suggest a relationship between intensity of care and 30-day cardiac outcomes.  Such intensity of care, however, is quite expensive – on the order of probably $1.5-$2M per life shortened and captured in this 30-day window.  As our population ages, we are simply going to have to do better – in order to maximize the value of the limited healthcare dollars.

“Variation in Chest Pain Emergency Department Admission Rates and Acute Myocardial Infarction and Death Within 30 Days in the Medicare Population”
http://www.ncbi.nlm.nih.gov/pubmed/26205260

The No-CT in Trauma Experience

In many trauma centers, the Emergency Department role is essentially: place an IV for which contrast may be delivered for CT.  Oh, yes, there’s some airway management, perhaps a FAST exam, some rolling and cutting of clothing, and the remainder of our expertise should not be diminished, but modern management has been distilled to: trauma = pan-scan.

Except in San Diego.

This fascinating paper describes 11 years of experience at a Level 1 trauma center in which the vast minority of their patients underwent automatic CT.  Between the hours of 8AM and 11PM, a resident and staff ultrasonographer were available for ultrasound examination of trauma patients.  At the discretion of the attending surgeon, the ultrasonographers performed an examination consisting of seven abdominal windows, bilateral visceral organ windows, and cardiac windows.

And, of the 19,126 trauma patients included in this study, essentially all patients presenting between 8AM and 11PM underwent this ultrasound.  Minus the 13 patients who went directly to the OR, this constitutes 12,565 patients initially screened with ultrasound.  Of these, 12,070 were judged to be negative examinations.  By the authors definition of false negative, a positive exploratory laparotomy finding, only 35 ultimately required such – a false negative rate of 0.29%.  Comparatively, CT was performed off-hours in 6,548 patients, and had a 0.1% false negative rate.

There were, of course, a mix of patients with positive ultrasound results who ultimately had negative CTs, and 1,119 negative ultrasounds who underwent CT with a 86 positive results.  So, there’s a lot of details and hidden corners to evaluate and analyze beyond their narrow definition.  But, still, impressively, their trauma protocol at a Level 1 center managed to spare half the patients the ubiquitous pan-scan.

Fascinating!

“Complete ultrasonography of trauma in screening blunt abdominal trauma patients is equivalent to computed tomographic scanning while reducing radiation exposure and cost”
http://www.ncbi.nlm.nih.gov/pubmed/26218686