2015 HSC Section 1 Book of Articles

B.

Collins

et al.

/ International

Journal

of Pediatric Otorhinolaryngology 78

(2014)

423–426

anterior parotid,

abscess lateral

[5] . As

this

study did not

include

abscesses

from

all of

the

and

posterior

triangles,

submandibular,

submental,

neck,

it

is

difficult

to

directly

compare

these findings with scans of deep and

and

parapharyngeal and demographic

spaces.

studies. A

similar

study of 16 CT

characteristics were

summarized

for

the ultrasounds

Clinical

neck

abscesses

demonstrated

a

sensitivity

of

91%

but

a

group

of

subjects

(CT

or

ultrasound).

The

mean

age

was

lateral

each

of

60%

[6] .

This

study was

limited

by

its

small

sample

between

groups

using

a

2-sample

t -test.

The

distribu-

specificity

compared

and mixed pathology. A comparison of ultrasound and CT in

of

gender was

compared

between

groups

using

a

Chi-square

size

tion

the diagnosis of pediatric

characteristics of

the CT and ultrasound groups

test. Demographic

abscesses

is necessary

in

order

to

establish

a practice

compared

after

excluding

patients who

underwent

both

CT

lateral neck

were

for

this

population.

CT

is

used

more

often

at

this

tests. The sensitivity, specificity, positive

guideline

and ultrasound screening

likely because

there

is a CT

technician available at

and negative predictive value were

calculated

for

institution, most

predictive value

all times whereas ultrasound readings are only available during the day. If it can be shown that ultrasound and CT are comparable in accuracy for the diagnosis of lateral neck abscesses, then a practice guideline can be developed based upon the cost and safety profiles of the two procedures. This study compares the accuracy of ultrasound and CT to the gold standard outcome of attempted drainage in order to promote judicious and individualized use of ultrasound and CT in the diagnosis of children with lateral neck abscesses.

separately.

The

accuracy

of

the

imaging method

is

each method summarized

using interval. Positive and negative predictive values were calculated assuming a positive abscess prevalence of 0.90. a two-sided 95% exact confidence

3. Results

One

hundred

thirty-two

patients

are

included

in

the

analysis

and 8

with 31 who underwent ultrasound, 93 who underwent CT,

and CT

scans. The median

age

of

who underwent both ultrasound

2. Materials

and methods

sample was

1.5

years

(range

one month deviation

to

18

years) with

a

the

age

of

2.9

years

(standard

3.5

years).

Although

mean

approval was

granted

by

the University

of Oklahoma

for

a

underwent

a

CT

scan were

on

average

one

year

older

those who

IRB

study

of

all

children

0–18

years

of

age with

lateral

than statistically significant. The gender distribution was well balanced between the groups ( Table 1 ). A total of 140 imaging studies were available for review, including 39 ultrasound studies with gold standard results of 34 positive and 5 negative and 101 CT studies with gold standard results of 90 positive and 11 negative. The overall prevalence of a pus-positive abscess in children undergoing the gold standard, incision and drainage, was 89%. Table 2 presents the estimated sensitivity, specificity, positive predictive value and negative predictive value for each method along with a 95% confidence interval for the estimate. The CT scan test method has very low specificity (2/11, 18%) and a very low negative predictive value (6%) assuming a positive abscess prevalence of 0.9. The sensitivity is reasonable (61/90, 68%). The positive predictive value (88%) is slightly lower than the assumed prevalence of 90%. Based on the assumed prevalence value, the probability of a pus-positive abscess is 90% (without knowledge of the CT test result) while the positive predictive value suggests that the probability of a pus-positive abscess is 88% among those with a positive CT scan. Similarly, the estimated negative predictive value (6%) is less than the assumed prevalence of a pus-negative abscess (10%). The ultrasound test method has a high estimated specificity (5/5, 100%) but a low sensitivity (18/34, 53%). The positive predictive value (96%) is high while the negative predictive value is low (16%) assuming a positive abscess prevalence of 0.9. Table 3 demonstrates the sensitivity and specificity of ultra- sound and CT by location of the abscess. Twelve of 140 imaging studies were excluded from this analysis because they included the ultrasound group, this difference was not

retrospective

abscesses

who

underwent

preoperative

imaging

prior

to

neck

an academic

tertiary

care

center

from 2005

attempted drainage at

2011.

This

allowed

evaluation

of

the

accuracy

of

CT

and

to

to the surgical finding of presence or absence of

ultrasound relative

the

gold

standard

for

determination

of

an

abscess.

To

pus,

power

the

study,

it

is

necessary

to

compare

appropriately approximately

40

ultrasound

and

40

CT

imaging

studies.

This

recommended

by

our

statistician

and

is

consistent with

goal was

power

of

previous

evaluations

of

CT

or

ultrasound.

Subjects

the

located by

a

search of

the medical

center billing database by

were

Procedural

Terminology

codes.

The

patients were

evalu- CT was

Current

in

two

groups

based

on whether

an

ultrasound

or

a

ated

prior

to

surgery.

There

are

no

specific children

preferences

performed

availability

that

determined which study. Currently

received

an

besides

in

this

there

is no

institutional

ultrasound or a CT protocol; rather

the decision

is influenced by when a child presents

which

physician

initially

sees

the

patient. When

clinically

and

some either

children imaging

are

taken

to

the operating

room without

indicated, receiving

study.

of

ultrasounds

and

CT

scans were

performed

at

The majority

institution

and

some

were

performed

at

outside

medical

this

prior

to

transfer.

All

imaging

studies

were

read

at

the the

facilities

tertiary care center. The

initial final report

from

same academic

of

radiology

was

used,

and

only

studies

performed drainages

department

3

days

of

surgery

are

included.

All

incision

and

within

were performed at this institution’s protocol, stable children presenting with suspected neck abscesses are given 48 h of intravenous clindamycin before drainage is attempted. Lateral neck abscess locations in this study include the facility. In accordance with this

Table 1 Demographic

characteristics

of

patients who

underwent

ultrasound

and

computed

tomography.

values a

patients b ( n = 132)

p -Value c (comparing

Baseline

All

Diagnostic

screening

approach

CT

to

ultrasound)

( n = 101)

Ultrasound

( n = 39)

CT

in

years

2.9 1.5

(3.5)

3.2 2.0

(3.5)

2.2 1.3

(2.9)

p = 0.16

Age

[0.04–18]

[0.08–18]

[0.04–16]

sex

69

(52%)

55

(54%)

19

(49%)

p = 0.53

Male

CT

–

computed

tomography;

–

total

number

in

category. deviation)

Legend:

n

a Distributions

summarized

using

the mean

(standard

and median

[range]

for

continuous measures

and

count

(column

%)

for

categorical measures.

b Data

are

available

for

132

patients, the mean

eight

of whom

underwent

both after

CT

and

ultrasound

screening.

c Statistical

comparisons

of

or

proportions were made

excluding

eight

patients

undergoing

both

CT

and

ultrasound

screening.

217