Preoperative Laboratory Testing in Patients Undergoing Elective,Low-Risk Ambulatory Surgery

Jaime Benarroch-Gampel, Kristin M. Sheffield, Casey B. Duncan, Kimberly M. Brown, Yimei Han,

Courtney M. Townsend, Jr., and Taylor S. Riall

Department of SurgeryCenter for Comparative Effectiveness and Cancer Outcomes

The University of Texas Medical BranchGalveston, TX

Which of the following preoperative laboratory test is routinely indicated in an 80 years old male undergoing low-risk ambulatory surgery

A.Complete blood countB.Chemistry panelC.Coagulation testsD.All of the testE.None of the test

• Ambulatory surgery

– <1-2 hours in duration

– Low expected blood loss

– Low complication rates

– Minimal expected postoperative care

– Performed in patients with no medical problems or stable chronic medical conditions

• 60-70% of procedures in the U.S. performed in the ambulatory setting

Preoperative Testing in Ambulatory Surgery

INTRODUCTION

• Potential benefits of preoperative testing

– Predicting patient risk for postoperative complications

– Screening for unsuspected abnormalities

– Establishing baseline values for tests that may change after surgery

– Providing medical-legal protection

Preoperative Testing in Ambulatory Surgery

INTRODUCTION

• Potential risks of preoperative testing

– Cost: estimated between 3-18 billion

– Increased pain and inconvenience

– Anxiety for patients

– Abnormal results in some cases are of questionable clinical significance

– Harm to patients due to overtreatment of false-positive results

– Medical-legal risk

Preoperative Testing in Ambulatory Surgery

INTRODUCTION

• Current recommendations based on 2002 Practice Advisory from American Society of Anesthesiologists (ASA)

– Based on expert opinion and underpowered studies

– Inconsistencies between societies

– Imprecise language

• Many advocate against routine testing

• Fail to outline clear and consistent guidelines for specific tests

Preoperative Testing in Ambulatory Surgery

INTRODUCTION

Preoperative Testing in Ambulatory Surgery

INTRODUCTIONINDICATION Hg/CBC Creatinine Electrolytes LFTs Albumin Coagulation

ParametersAdvanced age ASA

OPTGOPTG OPTG

Bleeding disorders

ASA ASACAS

OPTGCardiovascular

diseaseCAS

OPTGRenal disease CAS

OPTGCAS

OPTGASACAS

OPTG

ASA

Liver disease CASOPTG

OPTG ASACAS

OPTGHypertension OPTG CAS

OPTGCAS

OPTGDiabetes OPTG CAS

OPTGSmoking OPTG

Alcohol abuse OPTG OPTG OPTGASA: American Society of Anesthesiologists, CAS: Canadian Anesthesiologists’ Society, OPTG: Ontario Preoperative Testing Grid, LFT: Liver Function Tests

• Use population-based data (NSQIP) to: – Describe the current use of preoperative

testing in elective, low-risk ambulatory surgery

• All patients• Subgroup with no comorbidities

– Identify patient factors associated with preoperative testing

– Evaluate the association between preoperative testing and 30-day outcomes

Preoperative Testing in Ambulatory Surgery

OBJECTIVES

• National Surgical Quality Improvement Program Participant Use Data File (PUF)

• Study period: 2005-2010

• Contains 240 variables:

– Patient characteristics

– Procedure characteristics• Anatomic site• Open vs. laparoscopic• Initial vs. recurrent

Preoperative Testing in Ambulatory Surgery

METHODSData Source

• Inclusion criteria:

– >18 years old

– Elective hernia repair (CPT codes)• Inguinal hernia (49505, 49520, 49525, 49650, 49651)• Umbilical hernia (49585)• Epigastric hernia (49570)• Femoral hernia (49550, 49555)

– Same day admission

– No surgery in previous 30 days

– No additional surgical procedures at time of hernia repair

Preoperative Testing in Ambulatory Surgery

METHODSCohort Selection

Cohort Selection (continued)

• Preoperative testing defined as testing in the 30 days up to and including surgery

• Normal values were defined using our institutional laboratory ranges

Preoperative Testing in Ambulatory Surgery

METHODSLaboratory Testing

Hematology

HematocritWBC

Platelets

Hematology

HematocritWBC

Platelets

Chemistry

SodiumBUN

creatinine

Chemistry

SodiumBUN

creatinine

Coagulation

PTPTTINR

Coagulation

PTPTTINR

LFTs

AlbuminTotal bilirubin

ASTAlkaline

phosphatase

LFTs

AlbuminTotal bilirubin

ASTAlkaline

phosphatase

92% 90% 89%77%

• Additional outcome variables:

– Major complications: unplanned intubation, PE, stroke, coma >24h, acute renal failure, MI, cardiac arrest, sepsis/septic shock, blood transfusions, or death

– Wound-related complications: superficial and deep surgical site infections, organ space infections, and wound dehiscence

Preoperative Testing in Ambulatory Surgery

METHODS

• Use of preoperative testing described

• Chi-square to compare categorical variables and T-test to compare continuous variables

• Multivariate logistic regression models used to determine:

– Factors associated with preoperative testing

– Association between • Preoperative testing and 30-day outcomes• Abnormal results and 30-day outcomes

Preoperative Testing in Ambulatory Surgery

METHODSStatistical Analysis

NO LABS(N=26,619)

36%

LABS(N=46,977)

64%

P-value

PATIENT CHARACTERISTICSAge 48.6 ± 16.0 yrs 57.7 ± 15.9 yrs <0.0001Male gender 84.3% 84.4% 0.66White 82.7% 79.5% <0.0001ASA Class 3 11.4% 26.0% <0.0001At least 1 comorbidity 56.6% 71.1% <0.0001

PROCEDURE DETAILSGeneral anesthesia 76.1% 78.1% <0.0001Inguinal hernia 72.6% 74.5% <0.0001Laparoscopic repair 17.3% 18.4% 0.0002Recurrent hernia 6.7% 7.3% 0.001

RESULTSDemographics and Procedures

Preoperative Testing in Ambulatory Surgery

RESULTSPreoperative Testing Use

OVERALL COHORT (N=73,596)% Use % Abnormal

Any Test 63.8% 61.6%Hematology 58.6% 39.3%Chemistry 53.5% 40.2%Coagulation 18.7% 11.3%LFT 23.7% 22.8%

Preoperative Testing in Ambulatory Surgery

RESULTSPreoperative Testing Use

SUBGROUP WITHOUT COMORBIDITIESN=25,146 (34% of overall cohort)

% Use % AbnormalAny test 54.0% 54.1%Hematology 51.8% 36.2%Chemistry 41.8% 33.0%Coagulation 14.8% 5.9%LFT 19.6% 18.4%

Preoperative Testing in Ambulatory Surgery

RESULTSPreoperative Testing Use

SAME-DAY TESTING N=7,209 (9.7% of overall cohort)

% Use % AbnormalAny Test 100.0% 61.6%Hematology 86.0% 41.9%Chemistry 76.5% 40.9%Coagulation 35.4% 22.9%LFT 25.8% 33.2%

Preoperative Testing in Ambulatory Surgery

RESULTSPreoperative Testing Use

Age group All patients Without comorbidities

Younger than 20y 34.9% 33.5%21y – 30y 42.1% 40.0%31y – 40y 47.9% 43.7%41y – 50y 56.5% 49.9%51y – 60y 66.2% 58.5%61y – 70y 73.8% 66.3%71y – 80y 79.5% 71.8%

Older than 81y 83.2% 75.0%

Preoperative Testing in Ambulatory Surgery

RESULTSPreoperative Testing Use

RESULTSMultivariate Analysis: Factors Predicting Testing

• Factors associated with receipt of testing across all test types:– Increased age– Black or Hispanic race– ASA class 2 and 3– Receipt of general anesthesia– Laparoscopic procedures– Hypertension– Diabetes– Ascites– Bleeding disorders– Steroid use

Major Complications Wound-RelatedOR 95% CI OR 95% CI

OVERALL COHORTHematology 1.17 (0.88 – 1.56) 0.99 (0.83 – 1.18)

Chemistry 1.30 (0.97 – 1.75) 1.03 (0.87 – 1.24)

Coagulation 1.25 (0.93 – 1.67) 1.05 (0.84 – 1.30)

LFT 1.02 (0.77 – 1.36) 1.07 (0.88 – 1.30)

RESULTSAdverse Outcomes and Testing

• Major complications: 0.3% (N=239)• Wound complications: 0.8% (N=567)

Major Complications Wound-RelatedOR 95% CI OR 95% CI

SUBGROUP WITHOUT COMORBIDITIESHematology 0.77 (0.40 – 1.49) 1.36 (0.91 – 2.03)

Chemistry 1.00 (0.52 – 1.96) 1.35 (0.91 – 2.02)

Coagulation 1.38 (0.63 – 3.05) 1.04 (0.60 – 1.78)

LFT 0.94 (0.42 – 2.08) 1.07 (0.66 – 1.75)

Preoperative Testing in Ambulatory Surgery

RESULTSAdjusted Outcomes: Tested vs. Not Tested

Major Wound-relatedOR 95% CI OR 95% CI

ABNORMAL vs. NORMAL (Tested patients only)Hematology 1.29 (0.95 – 1.75) 0.96 (0.76 – 1.20)

Chemistry 1.28 (0.93 – 1.75) 1.15 (0.90 – 1.46)

Coagulation 1.52 (0.81 – 2.53) 1.16 (0.66 – 2.08)

LFT 1.50 (0.90 – 2.49) 1.14 (0.79 – 1.65)

Preoperative Testing in Ambulatory Surgery

RESULTSAdjusted Outcomes: Abnormal vs. Normal Tests

• Selection bias

• Unable to identify patients who had changes in planned surgery or repeat testing due to abnormal results

• NSQIP does not report all tests types

• Unable to identify ordering physician nor can we evaluate variation among providers

Preoperative Testing in Ambulatory Surgery

LIMITATIONS

Preoperative Testing in Ambulatory Surgery

MEDICARE TESTING RATESHERNIA REPAIR

TestAll patients(N=13,029)

No comorbidities(N=3,187)

Any test 84.5% 78.9%CXR 43.5% 38.1%EKG 62.0% 59.5%

Hg/Hematocrit 53.1% 49.6%Platelets 51.8% 48.3%

Creatinine 27.0% 23.2%Electrolytes 53.6% 48.2%

LFTs 35.2% 30.9%Coagulation 16.2% 9.2%

Preoperative Testing in Ambulatory Surgery

MEDICARE TESTING RATESARTHROSCOPY

TestAll patients(N=21,993)

No comorbidities(N=5,515)

Any test 81.2% 73.4%CXR 41.0% 34.9%EKG 57.6% 51.0%

Hg/Hematocrit 57.3% 49.1%Platelets 54.1% 46.0%

Creatinine 29.9% 24.9%Electrolytes 60.6% 50.4%

LFTs 35.9% 27.9%Coagulation 18.8% 12.4%

Preoperative Testing in Ambulatory Surgery

MEDICARE: VARIATION IN TESTING

Preoperative Testing in Ambulatory Surgery

MEDICARE: GEOGRAPHIC VARIATION

• Preoperative testing is overused

• Increased age was associated with increased rates of preoperative testing irrespective of presence of comorbidities

• Overuse of preoperative testing is not only limited to laboratory tests but include chest x-ray and EKG, both mostly used in the elderly

• Neither preoperative testing nor abnormal results were associated with worse outcomes

Preoperative Testing in Ambulatory Surgery

SUMMARY

• Future studies must evaluate the comparative effectiveness of testing for specific age groups

• Clear guidelines need to be developed for testing in the elderly

• Goals:– Decrease unnecessary testing – Decrease cost

• In order to succeed physician awareness must be increase and all parties must be willing to participate

Preoperative Testing in Ambulatory Surgery

CONCLUSIONS