Asymptomatic Bacteriuria in Adolescent Girls: II. Screening Methods

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Asymptomatic

Bacteriuria

in Adolescent

Girls:

II. Screening

Methods

S. Jean

Emans,

MD,

Estherann

Grace,

MD,

and

Robert

P. Masland,

Jr, MD

From the Division of Adolescent Medicine, Children ‘s Hospital Medical Center, and the

Department of Pediatrics, Harvard Medical School, Boston

ABSTRACT. Of 500 asymptomatic adolescent girls who

were screened for bacteriuria by three methods-dipslide

(Uricult), dipstrip (Microstix-3 reagent strips), and home

nitrite test (Microstix-Nitrite reagent strips)-eight cases (1.6%) weredetected: 6/8 by dipslide and dipstrip; 5/8 by

nitrite testing. The false-positive-rate (> iO colonies/mi) of the dipslide test was 6.4%, and the dipstrip test, 2.8%.

A history of vaginal discharge was not associated with

“contaminated” specimens. False-positive nitrite tests were reported by 0.6% of the patients who returned the

postcards.

Overall, 70.4% of the patients returned the postcards for the home nitrite test. The patients were divided by method of payment (Medicaid vs non-Medicaid) in order

to provide an approximation of socioeconomic status;

non-Medicaid patients were significantly more likely to return postcards than Medicaid patients (75.8% vs 63.7%). Of the group reporting previous urinary tract infection,

79% of both Medicaid and non-Medicaid patients

re-turned postcards, suggesting that a prior experience with

the diagnosis increased compliance with a home test.

Pediatrics 64: 00-00, 1979; bacteriuria, adolescent health care, screening costs, dipslide, dipstrip, nitrite test.

The techniques for screening urine for bacteriuria

have varied from traditional pour plate and quan-titative loop methods to dipstrip and dipslide cul-tures and the new nitrite indicator strips. In order to determine a simple cost effective means to detect asymptomatic bacteriuria (ABU) in adolescent fe-males, we planned to study three methods to assess

their advantages and disadvantages: (1) dipslide (Uricult-CLED

+

polymixin B/EMB, Orion Diag-nostica, Helsinki, Finland), (2) dipstrip

(Microstix-3 reagent strips, Ames Company, Div of Miles Lab,

Received for publication Nov 20, 1978; accepted Feb 5, 1979.

Reprint requests to (S.J.E.) The Adolescents’ Unit, Children’s

Hospital Medical Center, Boston MA 02115.

mc, Elkhart, IN), and nitrite indicator strips (Mi-crostix-Nitrite reagent strips, Ames Company). The first two methods were used in our clinic; the third method was used at home.

Dipslides have been widely used for the detection of bacteriuria. In a study of 340 patients, McAllister et al’ demonstrated that the dipslide had no false-negatives in contrast to the pour plate method. However, false-positives occur with contamination from the bacterial flora on the perineum.

With the dipstrip method the strip is similarly dipped directly into the patient’s clean voided urine and incubated. The strip has three reagent pads:

one for the recognition of nitrite, the second for

quantifying Gram-negative bacterial counts, and the third for quantifying total Gram-negative and Gram-positive bacterial counts. The nitrite test (de-scribed below) is recorded 30 seconds after the strip is dipped into the urine. The bacterial strips are read 24 hours after incubation. Each bacterial col-ony appears as a pink spot on the culture pad as a result of reduction of triphenyltetrazolium chloride. The strips are 88% to 89% accurate in detecting significant ur23

The nitrite strip detects bacteriuria by relying on the reduction of dietary nitrate in the urine to nitrite by Gram-negative bacteria. Sufficient num-bers of bacteria and adequate incubation time in the bladder are required for this chemical reaction. Testing the first morning urine voided on three

separate days resulted in one positive nitrite test in 85% to 88% of patients with proved significant bac-teriuria.3 The accuracy rises to 90% to 93% in pa-tients with bacteriuria caused by Gram-negative organisms. However, random urines in patients with documented urinary tract infections are posi-tive in only 20% of samples because of insufficient incubation time of the urine in the bladder.2

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ARTICLES 439

Adolescents’ Unit of Children’s Hospital Medical Center in which 500 adolescent girls were screened by the three methods described to determine relia-biity of case finding, relative cost, need for return

visits and reminders, patient compliance to a home

test, and effects of a history of vaginal discharge in the collection of a clean-voided specimen.

MATERIAL

AND METHODS

The methods are the same as those stated in part

I, Epidemiology (preceding article).

RESULTS

Of the 500 adolescent girls screened for asymp-tomatic bacteriuria by the three described methods, eight were diagnosed as having asymptomatic bac-teriuria: 6/8 patients were detected by dipslide and dipstrip and 2/8 initially had negative cultures but

were recalled because of a positive home nitrite test (Table). The repeat dipslide in cases 6 and 7 showed greater than i05 Escherichia coli/ml. Only one of

the eight patients had a positive nitrite test in our clinic. Five of the eight patients returned their postcards. Four had positive home nitrite tests. Patient 8 had had a positive nitrite test in clinic and was started on antibiotics for otitis media at the time of her clinic visit. In order not to influence

compliance, this patient was not told about the

results of the clinic nitrite test until after the

post-card was returned. The negative test confirmed

clearing of the bacteriuria. Thus relying on a method requiring home tests and return of post-cards, three patients with bacteriuria would not

have been detected compared to two patients

missed by the dipslide and dipstrip method.

Although two other adolescents reported 1/3 ni-trite tests positive, cultures done before and after the home test were negative. Thus, these two rep-resent either false-positives or transient bacteriuria.

Both of these patients were sexually active.

In this study, the dipslide and dipstrip were equally effective in recognizing patients with sig-nificant bacteriuria if all counts greater than iO

were reevaluated. The dipstrip did not detect 14

counts in excess of i0’ that were identified by the

dipslide. However, all of these were contaminated specimens with a negative follow-up dipslide test.

Although the small pads on the dipstrips were found

more difficult to read, they require less incubation

space than the dipslide. Forty dipslides (8%) were

read as having greater than 10,000 colonies/mi. Of

these, 34 were classified as false-positives; 15 had one or two organisms between iO and iO colonies/

ml, and 19 had one to five organisms greater than

io

colonies/rn!. Thirty-eight return visits were

nec-essary to establish a negative culture in the

false-positive group. Six dipslides with greater than iO E coli/ml were eventually shown to represent true

bacteriuria on the basis of repeat cultures or

posi-tive nitrite tests, or both.

A history of vaginal discharge was not associated with a significant increase in the incidence of

false-positives. Of the 22 patients reporting a discharge,

one (4.5%) had a dipslide with 20,000 to 100,000

colonies/mi and one had a dipslide with greater than i0 colonies/mi. In comparison, of the 478

patients without discharge, 14 (2.9%) had dipslides with 20,000 to 100,000 colonies/rn! and 18 (3.5%) had counts greater than iO colonies/rn!.

The home nitrite test demonstrated a high com-pliance response from the study group; 352 (70.4%)

patients returned the postcards, and 326 (65.2%)

returned them within 10 days of the visit. The distribution of patients by payment status showed

that 277 (55.4%) of the patients were non-Medicaid and 233 (44.6%) were Medicaid. Non-Medicaid

pa-tients had a significantly higher rate of postcard return than Medicaid patients, 75.8% vs 63.7%

(x2

= 8.72;

P

< .01). Only a small percentage of patients

(4.3% of non-Medicaid, 6.3% of Medicaid) returned the postcards after a reminder. Considering the

TABLE. Summary of Data for Eight Patients Detected with Asymptomatic Bacteriuria

Case

No.

Age (yr) Dipslide > 10 coi/ Dipstrip Positive Ni- Home Nitrite Test

ml E coli trite Test in

Clinic Postcards Results

Returned

1 12 + +

2 12 + +

3 13 + + Yes +2/3

4 14 + +

5 15 + + Yes +2/3

6 15#{189} Initial - - Yes + 2/3

Repeat +

7 17 Initial

-

Yes + 3/3

Repeat +

8 20 + + x Yes

*Positiv _{e nitrite} _test _{in clinic.} _Patient _treated _{for otitis} _media _with _antibiotic.

at Viet Nam:AAP Sponsored on September 7, 2020 www.aappublications.org/news

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expense involved, this was not considered a feasible procedure. Of the subgroup of 47 patients reporting a previous urinary tract infection (UT!), 37 (79%)

returned their postcards within 10 days. Medicaid

patients with a history of UT! returned postcards

as frequently as non-Medicaid patients with a sim-ilar history and more frequently than Medicaid

patients without previous UTI’s (79% vs 63%). Be-cause of small numbers the latter figures did not

reach statistical significance.

The patient’s comments on the postcards were

favorable-”easy,” “much better than giving a urine

in clinic,” “simple.” There were no negative

corn-ments other than the failure of 29% to comply. The

two reasons most frequently given to the nursing

assistant who contacted these patients were “I for-got” and “I lost it.”

Overall cost of a screening method is an impor-tant consideration in determining its suitability for

clinical application. The costs of the methods used in this study are $0.63/dipslide, $0.86/dipstrip, and $0.84/3 nitrite strips (the price of the latter two might be influenced by bulk ordering). If a postcard

were included, the home test would cost an

addi-tional $0.10. The time collecting the urine speci-rnens and reading either a dipslide or dipstrip in the clinic was comparable to the time for giving

instruc-tions to the patient for a home test. Thus the overall

cost of detecting a patient with ABU is the cost of

the initial screening method plus the repeat cultures

(by dipslide) plus bacteriology fees for cultures read

as positive. In our hospital the charge is $15 for identification of the organism and $10 for the

sen-sitivity tests. Since the cost for return visits,

park-ing, money lost from time off at work for patient and/or parent is variable, no dollar figure is at-trached to these hidden costs; however, these issues are an important consideration in a physician’s decision to use a particular method. It should be noted that all three methods are suitable for home

use.

In the figures given below, we calculated costs on the basis of the number of repeat dipslides

neces-sary to establish bacteriuria. For example, with dipslides, 38 repeat cultures were necessary to

es-tablish a negative culture in 34 patients with

ii-tially false-positive urine tests; 12 repeat cultures would be necessary to rnake the diagnosis of ABU in the six patients detected. In contrast, if dipstrips were used, 24 repeat cultures would be necessary for patients with false-positive dipstrip tests and 12

cultures for those with true-positive results. Since nitrite testing yields few false-positive results, only two cultures were necessary for false-positive and five cultures for true-positive tests, considerably

reducing bacteriology charges. The cost of detecting one patient with ABU is thus the cost of screening

divided by the number detected: (1) dipslide

$1,246.50 + 6 = $207.75; (2) dipstnp $1,142.68 + 6

= $190.45; (3) nitrite strips $625.00 #{247}5 = $125.00

(including postage). The cost per positive result is based on screening all adolescent girls; in fact, our current recommendations, based on a prospective study of epidemiology, has led us to recommend screening only those with a history of UT! or other urinary tract problem. If five patients were detected from these 48 screened (47 with past history of UT! and one with a structural abnormality), the cost per

positive result would be (1) dipslide $358.43 + 5 =

$71.69; (2) dipstrip $338.21 - 5 = $67.64; (3) nitrite

strips $173.27 #{247}5 = $34.65.

DISCUSSION

Each of the three screening methods used in this

study has advantages and disadvantages. The dip-slide and dipstrip can be used in a clinic, school, or

home setting. Unfortunately, the rate of contami-nation is appreciable. Freeman and Sindhu4 found

that of 7% of school girls with greater than l04colonies/rnl and 4% greater than i0 colonies/mi only 1.5% were bacteriuric. Similarly, Kunin and DeGroot3 found a false-positive rate (greater than

io

colonies/mi) of 1.0% for dipstrips and 10.6% for the pour plate method. In our study the dipslide

gave a false-positive rate of 6.8% compared to the

dipstrip of 2.8%. Symptomatic vaginal discharge did

not increase the false-positive rate of the dipslide.

Since contaminants are detected more frequently by the pour plate method, the use of the dipstrip tends to reduce the need for return visits. Although

in our study all six patients detected by dipslide were also detected by a dipstrip with greater than iO colonies/mi, Kunin found only 88% of women with bacteriuria were detected by dipstnp.

A surprising finding was that 2/8 cases were not detected by direct culture. The urine specimens

were collected under random circumstances, not first morning specimens, so a dilute urine or urine

in a patient who had recently voided might give a

low count considered to be negative (10,000

cob-nies/ml or less) in a clinic. Since the dipslide and dipstrip were done on one day and the home nitrite test on the three days following the visit, it is also possible that these two patients developed bacteri-uria subsequent to the visit. In fact, patient 6 had

positive nitrite tests on days 2 and 3, but not day 1

of her testing. Previous studies to compare nitrite

tests with direct urine cultures have either used known bacteriuric patients for nitrite screening or have collected a first morning urine for direct

cub-ture the same day as day 1 of the nitrite test.

The nitrite testing method has been well

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ARTICLES 441

Since most cases of ABU are caused by E

coli-81% in data by Kunin and DeGroot,3 91% in the Newcastle study,5 and 100% in our report-the ni-trite strips should give a high yield of cases. Unfor-tunately, the test relies heavily on motivation. The teenagers in our Unit did as well in initial return of the test (65.2%) as did a group of mothers screening their 3- to 5-year-old daughters (65.7%).6 In the

group with the past history of UTIs, 79% returned the cards within 10 days indicating that prior

ex-perience with diagnosis increased compliance. We noticed that the return of nitrite test postcards was significantly better than the return of Tine test

postcards in our Unit: only 32 of 100 adolescents

returned these cards within one month of the visit (S. Emans and E. Grace, unpublished data).

Thus the low risk adolescent (asymptomatic, his-tory of UT! more than two years previously) can

be screened with either a dipslide or a home nitrite test. Physicians without easy access to a bacteriol-ogy laboratory may find it simpler to use nitrite testing in motivated adolescents. In adolescents

with recurrent UTIs and asyrnptomatic youngsters with renal scarring or reflux, or both, combined home testing can be done every three months or at

the first sign of symptoms with a first morning

dipslide and nitrite test. The dipslide is incubated on the stove or refrigerator top and read by the youngster 24 hours later by comparing it to the two

nitrite tests already done. Depending upon the test

results, she can call in for treatment and mail the

dipslides. This has the advantage of early diagnosis and essentially no false-positives.

ACKNOWLEDGMENT

We thank The Ames Company, Elkhart, IN, for

pro-viding nitrite strips, dipstrips, and the stamped postcards.

REFERENCES

1. McAllister T, Arneil G, Barr W, et al: Assessment of plane

dipslide quantitation of bacteriuria. Nephron 11:111, 1973

2. Gillenwater J, Gleason C, Lohr J, et al: Home urine cultures by the dipMrip method. Pediatrics 58:508, 1976

3. Kunin C, DeGroot, J: Self-screening for significant

bacteri-uria. JAMA 231:1349, 1975

4. Freeman J, Sindhu S: A survey for bacteriuria in school girls.

MedJAust 1:135, 1974

5. Newcastle Asymptomatic Bacteriuria Research Group: . Asymptomatic bacteriuria in school children in Newcastle

upon Tyne. Arch Dis Child 50:90, 1975

6. Kunin C, DeGroot J, Uehling D, et al: Detection of urinary

tract infections in 3- to 5-year-old girls by mothers using a nitrite indicator strip. Pediatrics 57:829, 1976

THE MOST CAPTIVE CONSUMERS

Wheelchair users’ lives are shaped by an ironic disparity in technologies. The

last two decades have produced medical advances which mean that many injuries that once meant death now mean survival in a wheelchair. But there

has not been a comparable advance in devices that improve life for the survivors. The significant advances in the technology of improved medical treatment are the result of research heavily subsidized by billions of taxpayers’ dollars. By

comparison, the technology of making life tolerable for the survivors has been the Government’s neglected afterthought. Submitted by Student

From Medsger, B.: The most captive consumers. The Progressive, March 1979, p 34.

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1979;64;438

Pediatrics

S. Jean Emans, Estherann Grace and Robert P. Masland, Jr