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913Vol. 212, No. 5, May 2011 Letters

internalized memory of the standard laparoscopic para-digm in more experienced surgeons together with a poten-tial bias against a recent—for some, awkward—“trend” ofinverted ambidexterity might be the cause for our observa-tion. However, because we did not train the “dogs” but onlyassessed initial performance differences, any conclusionabout whether “old dogs” can or cannot be taught “newtricks” should not be drawn based on our study. On theother hand, we believe that surgeons, independent of age,can push their own boundaries and are able to becomeproficient in novel surgical procedures by appropriatelypracticing “new tricks” during preclinical simulations, suchas is now required during standard laparoscopy training.5

REFERENCES

1. Rieder E, Martinec DV, Casera MA, et al. A triangulating oper-ating platform enhances bimanual performance and reduces sur-gical workload in single-incision laparoscopy. J Am Coll Surg2011;212:378–384.

2. Sariego J, Spitzer L, Matsumoto T. The “learning curve” in theperformance of laparoscopic cholecystectomy. Int Surg 1993;78:1–3.

3. Dapri G, Casali L, Bruyns, et al. Single-access laparoscopic sur-gery using new curved reusable instruments: initial hundred pa-tients. Surg Technol Int 2010;20:21–35.

4. Salkini MW, Hamilton AJ. The effect of age on acquiring laparo-scopic skills. J Endourol 2010;24:377–379.

5. Okrainec A, Soper NJ, Swanstrom LL, Fried GM. Trends andresults of the first 5 years of Fundamentals of Laparoscopic Sur-gery (FLS) certification testing. Surg Endosc 2010 Sep 25. [Epubahead of print].

Disclosure Information: Nothing to disclose.

The Impact of Select ChronicDisease on Outcomes after Trauma

Russell Griffin, MPH, Gerald McGwin Jr, MS, PhD

Birmingham, AL

We read with great interest the recent study report by Pateland colleagues,1 in which the authors examined the rela-tionship between chronic comorbid conditions (CMCs)and outcome among trauma patients using the NationalTrauma Data Bank. First, the authors failed to cite a previ-ously published report on the relationship between CMCsand mortality using this same database2; as a result, theyailed to demonstrate how their analysis extends this priorork. Second, there are some concerns regarding the study

esign that may affect the interpretations of the data.

Foremost, although the authors stated that a case-atched control design was used, they matched individualsith a given CMC (ie, exposed individuals) to those with-ut a given CMC (ie, unexposed). As a result, this design isore accurately described as a matched cohort study; how-

ver, it should be noted that matching in a cohort studyoes not necessarily remove the effects of a confounder.3

That is, matching in observational studies is not similar tomatched randomization (ie, blocking) in clinical trials.4

Although matching may control for the confounders in thecohort before follow-up, the association between exposureand confounders may change during the follow-up periodas individuals are lost from the cohort owing to either get-ting the outcome of interest or dying.3 This results in apossible decrease in statistical efficiency and an increase intype II error because these factors must be additionallycontrolled for in regression models. Therefore, an un-matched design, using regression techniques to adjust forthe matching factors, may have been more efficient, partic-ularly given the availability of the data. This would addi-tionally allow variables such as injury severity to be exam-ined as an effect modifier for the association betweenCMCs and trauma outcome, as suggested by the aforemen-tioned previously published work using the NationalTrauma Data Bank.2

Finally, the analysis of the study is problematic in thatnone of the techniques addressed the difference in time atrisk (ie, days hospitalized) between exposed and unexposedindividuals. As shown in Tables 2 through 5, the exposedcohorts had a longer length of stay, which presented agreater opportunity to develop the outcome comparedwith the nonexposed cohorts. Therefore, any increased riskassociated with CMCs may be more a function of theirlonger exposure to risk than something inherent to theCMCs themselves. Instead, the authors should have used amethod for cohort studies that can account for thematching—and control for unmatched confounders—such as a Cox regression or conditional Poisson regression.

We hope that the authors address the concerns presentedin this letter, and we look forward to reading the revisedresults.

REFERENCES

1. Patel MS, Malinoski DJ, Nguyen XMT, Hoyt DB. The impact ofselect chronic diseases on outcomes after trauma: a study from theNational Trauma Data Bank. J Am Coll Surg 2011;212:96–104.

2. McGwin Jr G, MacLennan PA, Fife JB, et al. Preexisting condi-tions and mortality in older trauma patients. J Trauma 2004;56:1291–1296.

3. Rothman KJ, Greenland S. Modern Epidemiology. 2nd ed. Phil-

adelphia: Lippincott Williams & Wilkins; 1998.

914 Letters J Am Coll Surg

4. Greenland S, Morgenstern H. Matching and efficiency in cohortstudies. Am J Epidemiol 1990;131:151–159.

Disclosure Information: Nothing to disclose.

Reply

Madhukar S Patel, ScM, Xuan-Mai T Nguyen, PhD

Orange, CA

Darren J Malinoski, MD

Los Angeles, CA

David B Hoyt, MD, FACS

Chicago, IL

We thank Griffin and McGwin for their critique and inter-est in our work1 and congratulate them on their previouscontribution in this area.2

Our use of the term case-matched control study was in ageneric sense. We agree that a regression model could havebeen used in this study; however, 2:1 matching based onpotentially confounding variables is also an appropriateapproach because confounding can be controlled eitherduring the analysis phase (ie, in a regression model, assuggested) or during the design phase (ie, in the case-matched control method used in the current study1).3

In addressing the difference in time at risk (ie, days hos-pitalized), a clarification should be made. Given the limi-tations of the National Trauma Data Bank, it is not possibleto know whether a difference in time at risk is the cause orconsequence or is unrelated to a specific outcome (eg, mor-bidity or mortality). Time of hospitalization is also con-founded by variability in the time to discharge to nursinghomes or rehabilitation, which is highly variable amongtrauma centers. Additional clinical information, detailingthe course of the hospital stay for each patient, would berequired before being able to potentially suggest an expla-nation, or lack thereof, for the noted increase in hospitallength of stay in trauma patients with preexisting cirrhosis,dialysis, and HIV/AIDS (Tables 2–4) and the lack of dif-ference noted in patients on preinjury warfarin therapy(Table 5).1

Once again, we thank Griffin and McGwin for the timethey have taken to address our study as well as provideimportant methodologic suggestions, and we appreciate

their contribution to this important field.

REFERENCES

1. Patel MS, Malinoski DJ, Nguyen XM, et al. The impact ofselect chronic diseases on outcomes after trauma: a study fromthe National Trauma Data Bank. J Am Coll Surg 2011;212:96–104.

2. McGwin G Jr, MacLennan PA, Fife JB, et al. Preexisting condi-tions and mortality in older trauma patients. J Trauma 2004;56:1291–1296.

3. Aschengrau A, Seage GR. Essentials of Epidemiology in PublicHealth. Sudbury, MA: Jones and Bartlett; 2003.

Disclosure Information: Nothing to disclose.

The Diverse Surgeons Initiative andIncreasing UnderrepresentedMinorities in Academic Surgery

Mallory Williams, MD, MPH, FACS

Toledo, OH

I read with great interest the article by Butler and col-leagues1 regarding increasing the number of underrepre-sented minorities in academic surgery. This descriptive ret-rospective analysis of a preselected cohort of minoritysurgery residents demonstrated that 86% of participantsreceived surgical fellowship training and greater than 50%of participants achieved academic positions. This is excit-ing, considering that African Americans and Latino Amer-icans comprise 4.7% and 5.1% of surgery residents andonly 2.9% and 3.6%. of academic surgeons, respectively.2

But the follow-up data on these individuals’ academic ca-reers are desperately needed. What academic rank do theseindividuals currently hold and at which institutions? Aresome serving in leadership positions? It would seem thatthis group of individuals could serve in a longitudinal co-hort study. The attrition rate of junior surgery faculty iswell described and particularly salient among minority sur-gery faculty. How many of this talented group are currentlyinvolved in successful mentor relationships? Do these indi-viduals require additional interventions to ensure their suc-cess? What should these interventions accomplish? Can welearn from this seemingly successful program and its par-ticipants through future survey data? Perhaps small clues tofinding the holy grail of preparing, recruiting, retaining,and promoting underrepresented minority surgery facultyhave been discovered. I would like to congratulate the au-thors on producing one of the very few reports that at-tempts to pierce the very difficult issue of underrepresented

minority participation in academic surgery.