AFRICAN JOURNAL OF CLINICAL AND EXPERIMENTAL MICROBIOLOGY MAY 2011 ISBN 1595-689X VOL 12 No. 2
AFR. J. CLN. EXPER. MICROBIOL. 12(2):62-66
DIAGNOSTIC ACCURACY OF RAPID UREASE TEST FOR THE DIAGNOSIS OF
HELICOBACTER PYLORI IN GASTRIC BIOPSIES IN NIGERIANS WITH DYSPEPSIA
Jemilohun1, A.C., Otegbayo2, J.A ., Ola2, S.O., Oluwasola3, A.O. and Akere2 ,A.
1Department of Medicine, Federal Medical Centre, Iddo- Ekiti, Nigeria, 2Department of Medicine, College of
Medicine, University of Ibadan and University College Hospital, Ibadan, Nigeria, 3Department of Morbid
Anatomy and Histopathology, College of Medicine, University of Ibadan and University College Hospital,
Correspondence: Dr A.C. Jemilohun, Federal Medical Centre, Iddo- Ekiti, Nigeria, P.M.B. 201, Iddo-Ekiti, Ekiti
State, Nigeria.Email:firstname.lastname@example.org. Tel: 08038674623
Running title: DIAGNOSTIC ACCURACY OF RAPID UREASE TEST
Background: The strong association of Helicobacter pylori (H. pylori) with dyspepsia has caused a major paradigm shift in
patients’ management. It has been observed that histology is usually employed as the routine test for the diagnosing H.
pylori in centres where Oesophagogastroduodenoscopy (OGD) is available in Nigeria. Because of the drawbacks attendant
to the use of histology, in terms of cost effectiveness and technical expertise, it is necessary to evaluate the diagnostic
accuracy of a simpler alternative for ease of management of patients with dyspepsia.
Objective: This study evaluated the diagnostic accuracy of rapid urease test (RUT) in the diagnosis of Helicobacter pylori (H.
pylori) in patients with dyspepsia.
Methods: Eighty-six consecutive adult patients with dyspeptic symptoms presenting for endoscopy were recruited after
giving informed consent. Gastric antral biopsies were collected at endoscopy for RUT and histology. Sensitivity, specificity,
positive predictive value (PPV), negative predictive value (NPV) of RUT was calculated using histology as the reference
Results: Of the 86 subjects, there were 39 (45.3%) males and 47(54.7%) females. The mean age was 49.19±13.75 years. The age
range was 23 to 85 years. The sensitivity, specificity, PPV, NPV of RUT was 93.33%, 75.6 %, 80.76 %, and 91.17 %
Conclusion: RUT is accurate for the diagnosis of H. pylori infection. Its use will serve as a good alternative to histology in
management of patients with dyspepsia in resource poor environments, except in patients who need histology for reasons
other than H. Pylori diagnosis.
Key words: Dyspepsia, Helicobacter pylori, Rapid Urease test, Histology.
LIST OF ABBREVIATIONS
Helicobacter pylori is a gram negative, spiral,
flagellated bacterium with the capability of
abundant urease production. H. pylori bacterium is
usually found under the mucus layer in the gastric
pits and in close apposition to gastric epithelial cells
(1). Since the discovery of H. pylori by Warren and
Marshall (2), it has been evidently demonstrated
that the organism plays a major role in several
upper gastrointestinal diseases which present as
dyspepsia (2- 4). Helicobacter pylori infection causes
chronic active gastritis in the antrum (antral
gastritis), the corpus (corpus gastritis) or in both
(pangastritis). It is a major aetiological factor in
peptic ulcer disease, gastric carcinoma, and gastric
mucosal associated lymphoid tissue (MALT)
lymphoma (2, 5, 6). Haemorrhage and perforation
Haematoxylin and Eosin
Negative predictive value
Positive predictive value
Rapid urease test
are the most frequent complications of peptic ulcer
disease and are associated with substantial
morbidity, mortality and health care costs (6). Peptic
ulcer disease can be cured by eradicating H. pylori
so that complications no longer occur (1).
There are various diagnostic tests for H. pylori which
can be broadly classified into invasive and non-
invasive tests (7). Invasive tests utilise endoscopic
gastroduodenal biopsy samples for histology,
culture, rapid urease test (RUT), polymerase chain
reaction and fluorescent in-situ hybridization. The
non-invasive tests do not require endoscopy; they
include urea breath test, immunoglobulin G, A and
M serology, stool antigen test, saliva antibody test
(8, 9) and urinary antibody test (10). In Nigeria, the
non-invasive tests are not generally available with
the exception of IgG serology. Serological screening
is of limited value, especially in a hyper-endemic
area like Nigeria, because it has low discriminatory
the routine test for diagnosing H. pylori. There are
relatively few histopathologists in Nigeria, and they
are usually concentrated in government owned
Teaching Hospitals located in urban centres.
Histology report on gastric mucosal biopsies for H.
pylori usually takes two weeks or more to be
available while RUT results for H. pylori could be
read within 5 minutes to 24 hours of test (11). The
RUT is also much cheaper compared to histology
for H. pylori diagnosis, as the test is carried out in
the endoscopy suite by the Endoscopist or an
assistant. There has been a recent modest increase
in the availability of gastrointestinal endoscopic
facilities and it is envisaged that more centres with
no histopathology services will begin to have such
facilities as expertise increases in Nigeria. In view of
the foregoing advantages of the RUT, and the
generally low socioeconomic status of majority of
the Nigerian populace, it is desirable to evaluate
RUT diagnostic accuracy using histology as the
MATERIALS AND METHODS
The study was carried out at the Endoscopy sub-
unit of the Gastrointestinal & Liver Unit,
Department of Medicine, University
Hospital, Ibadan, Nigeria. Ethical approval was
sought and obtained from the Joint University of
Ibadan/ University College Hospital Institutional
Review Committee. Eighty- six consecutive adult
patients with dyspeptic symptoms presenting for
OGD were recruited after giving informed consent.
Diagnosis of dyspepsia was made clinically
according to the Rome working teams’ definition
(12). Patients’ symptoms had persisted for a
minimum of 3 months or recurrent in nature for the
same period. Those who were previously treated
for H. pylori infection or who had received
antibiotics, proton pump inhibitors or bismuth
compounds in the preceding 4 weeks were
excluded. Base line bio-data were obtained.
OGD was performed on all the participants using
Olympus (GFI-XQ20) or Pentax (FG29W) forward-
patients had pharyngeal spray with 2% xylocaine.
Most of the patients had conscious sedation with
pentazocine. All were
multiparameter pulse oximeter(EDANinstruments).
power between previous and current infection.
Centres that have OGD usually employ histology as
Two gastric antral mucosal biopsies were taken for
each of RUT and histology.
Rapid urease test (RUT)
Two of the four antral biopsies taken from each
patient were used immediately for RUT. The RUT
consisted of two dry filter paper containing urea,
phenol red (a pH indicator) in a sealed plastic slide.
If the urease enzyme of H. pylori was present in an
inserted tissue sample, the resulting decomposition
of urea to CO2 and NH3 caused the pH to rise and
the colour of the dot turned from yellow to a bright
magenta. Results were read within 3 hours after
sampling according to
specification. The colour change from yellow to
magenta was considered a positive result while no
colour change was regarded as negative.
The other two antral biopsies were fixed in 10%
formaldehyde and transferred to the histopathology
laboratory for processing. Four micron thick
paraffin sections were stained with routine
Haematoxylin and Eosin (H&E) for detection of H.
pylori and gastritis. Giemsa stain which is a special
histochemical stain for H. pylori was also used for
better yield. Slides were examined microscopically
for H. pylori by the help of a Gastrointestinal
Pathologist. The presence of submucosal helical
(Helicobacter-like) organisms was regarded as
positive while its absence was regarded as negative.
Data was analyzed using Statistical Package for
Social Sciences, version16.0 (SPSS Inc. Chicago
Illinois). Results were presented as means ±
standard deviation for quantitative variables and
number (percentages) for qualitative variables.
predictive values of RUT was calculated by two by
two standard method.
A total of 86 adult patients with dyspepsia
participated in the study. The mean age
was 49.19 (±13.75) years. There were 39
(45.3%) males and 47(54.7%) females. The
minimum age was 23 years and the
maximum was 85 years. The results of the
diagnostic tests are shown in table 1. The
RUT was positive in 52 (60.5 %), while
histology was positive in 45(52.35%).
positive and negative
TABLE1: RESULTS OF RAPID UREASE TEST AND HISTOLOGY IN SUBJECTS
Rapid urease test
52 (60.5 %) 34(39.5 %)
TABLE 2: COMPARISON BETWEEN RUT AND
Rapid urease test
+ve 42 10 52
TABLE 3: DIAGNOSTIC ACCURACY OF RUT
-ve 3 31 34
45 41 86
VALUE % 95% C. I.*
*C. I. = Confidence Interval
Table 2 shows the comparison between results of
RUT and histology. The total number of those
who were both positive for RUT and histology
(true positive) was 42(48.84%), those who were
positive for RUT but negative for histology (false
positive) were 10(11.62%), those that were both
negative for RUT and histology (true negative)
were 31(36.04%), while those that were positive
for histology but negative for RUT (false
negative) were 3 (3.49%).
The sensitivity, specificity, PPV and NPV of RUT
were 93.33%, 75.6 %, 80.76 %, and 91.17 %
respectively (table 3).
The diagnosis of H. pylori by culture, gram stain
and histology, which are biopsy based methods,
is well established. However, several drawbacks
attend to them. Firstly, the delay in the
availability of results, and secondly the rarity of
laboratory support especially in developing
countries like Nigeria. Other problems associated
with histological diagnosis of H. pylori arise
because the result depend on the competence of
the pathologist, the time spent to examine the
variability of staining techniques (11, 13). Special
stains for biopsy specimens improve visual
detection of the bacteria. To mitigate these
problems in our study, the service of a
Gastrointestinal Pathologist was employed and
Giesma stain was used in addition to routine
H&E. Giemsa stain is the most frequently used
stain for H. pylori diagnosis in routine clinical
variability) and the
practice, because of its diagnostic performance
and lack of technical difficulty in preparation in
comparison with the other stains (13, 14). A
major advantage of histological examination over
other biopsy based methods is that it also
provides information about gastric mucosal
The RUT practically overcomes these drawbacks
since it is not dependent on the experience and
accuracy of individual laboratories as in the case
of other biopsy based methods. As usefully and
attractive as RUT is, it has its own draw backs. In
theory, patients that salivate or have reflux
alkaline bile into the stomach could have a weak
positive reaction because the liquid may
contaminate a small gastric biopsy specimen such
that the resulting surface pH is >6.0 (6). Similarly,
chronic use of proton pump inhibitor may lead to
achlorhydria and subsequent
colonisation of the gastric mucus layer with
urease-producing organisms e.g. Klebsiella or
Proteus mirabilis (1, 6).These organisms can give a
false-positive urease test after 24 hours of
inoculation but generally negative tests remain
so when read within the specified time by the
manufacturer (6, 15).
It has been shown that the use of proton pump
inhibitors increases the numbers of false-negative
tests (16). Two possible mechanisms by which
this is done have been identified. Firstly, the
medication may directly inhibit H. pylori urease
activity. Secondly, the changing patterns of H.
pylori colonisation after acid suppression may
delay the positivity of RUT. Helicobacter pylori
often only resides in the corpus during long-term
use of proton pump inhibitors and can therefore
not be detected in antral biopsies (16). The
problem of chronic proton pump inhibitor use
was avoided in our study by excluding patients
who were on the drug in the preceding four
weeks to the test.
The presence of blood may also adversely affect
the performance of RUT leading to a false
negative result. This is due to the buffering
effect of serum albumin on the pH indicator,
rather than by a direct inhibition of the urease
Rapid urease tests have specificity and sensitivity
of greater than 90%, but false-positive results do
occur (17). The RUT had a sensitivity and
specificity of 97.4 and 96.1% respectively in an
earlier study conducted by van Keeken et al. (6) in
the Netherlands. The relatively lower values
obtained in our study compared to that of van
Keeken et al. and other previous similar studies
(13,18, 19, 20) could be explained by the fact that
they all used more than one diagnostic method as
reference standard, as no single presently
available test provides the definitive diagnosis of
H. pylori by itself (13, 21). For instance, van
Keeken et al. used a combination of histology and
culture as the reference standard in their study.
The implication of this is that any infection
missed by one test due to the patchy distribution
of the infection and consequent sampling error
could be easily picked by the other tests, thereby
increasing the number of positive results by the
reference standard. This is further buttressed by
the fact that there were less positive results by
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We declare no conflict of interest
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