COMPARISON OF DIPSTICK URINALYSIS WITH URINE CULTURE IN THE DIAGNOSIS OF ASYMPTOMATIC BACTERIURIA AMONG PREGNANT WOMEN ATTENDING ANTENATAL CLINIC IN PLATEAU STATE SPECIALIST HOSPITAL, JOS

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COMPARISON OF DIPSTICK URINALYSIS WITH URINE CULTURE IN THE DIAGNOSIS OF ASYMPTOMATIC BACTERIURIA AMONG PREGNANT WOMEN ATTENDING ANTENATAL CLINIC IN PLATEAU STATE SPECIALIST HOSPITAL, JOS

 

SUMMARY

Background: The study was prompted by the search for a test which could be equal to or better in diagnostic accuracy than quantitative urine culture, but less expensive or complex in the detection of asymptomatic bacteriuria among pregnant women.

Objective: The objective of the study was to establish whether the diagnosis of ASB in pregnancy by dipstick urinalysis among booked ANC women at Plateau State Specialist Hospital Jos was comparable to urine culture as gold standard.

Design: The study was a facility-based descriptive cross-sectional study. The sampling method was non-probability convenience sampling.

Subjects: This consisted of 124 pregnant women who presented for antenatal care visits. They were between the ages of 17-43 years and gave informed consent.

Methods: With the aid of a questionnaire patients who were screened into the study had their socio-demographic data and relevant current and past medical history recorded. A physical examination was carried out measuring their temperature, eliciting for lower abdominal tenderness, renal angle tenderness and noting the fetal heart sounds. Urine samples for urinalysis and urine culture were obtained using the clean catch mid urine technique. A positive leukocyte esterase test of; +, ++ or +++, equivalent to leucocytes counts of 25 WBC/µm, 75 WBC/µm or 500 WBC/µm respectively and/or a positive nitrite test was considered a positive test for dipstick urinalysis and a single colony count of 105 was considered significant for urine culture.

Results: The prevalence of ASB by urine culture was 26.6%, and the prevalence by dipstick urinalysis was 13.7%. Escherichia coli was the most frequently isolated pathogen n = 22 (66.7%) followed by Staphylococcus aureus 9 (27.3%), then Proteus spp 1(3%) and Klebsiella 1(3%). The number of times patient had sexual intercourse in the preceding week was found to be associated with ASB in pregnancy by dipstick urinalysis. An increasing gestational age was found to be associated with ASB in pregnancy by urine culture. The result of association between dipstick urinalysis and urine culture showed a statistically significant association between these two (p-value 0.01). Using urine culture as a gold standard, the statistical indices of disjunctive pairing of dipstick urinalysis (LE or nitrite) were prevalence, 13.7%; sensitivity, 36.4%; specificity, 94.5%; PPV, 70.6%; NPV, 80.4%; and accuracy, 79.0%, while that of the conjunctive pairing of dipstick urinalysis (i.e both nitrite and LE positive) were prevalence, 2.4%; sensitivity, 6.1%; specificity, 98.9%; PPV, 66.7%; NPV, 74.4%; and accuracy, 74.2%.

Conclusion:  A disjunctive pairing (i.e dipstick positive when either nitrite or LE or both are positive) is most suggestive of ASB when dipstick urinalysis is used as a screening test in pregnancy than the conjunctive pairing of dipstick urinalysis (i.e both nitrite and LE being positive). For poor resource settings, the use of a disjunctive pairing of dipstick urinalysis would be favoured because of the beneficial effect of treating more women for ASB and the relatively lower risk of treating patients who are false positive results.

 

TABLE OF CONTENT

Declaration………………………………………………………………………………………………………………….i

Acknowledgement …………………………………………………………………………………………………….. ii

Dedication ………………………………………………………………………………………………………………. iii

Certification I (Supervisors)……………………………………………………………………………………….. iv

Certification II (Head of Department)…………………………………………………………………………… v

Table of Content……………………………………………………………………………………………………….. vi

List of Tables …………………………………………………………………………………………………………….xi

List of Figures ………………………………………………………………………………………………………… xii

List of Abbreviations ……………………………………………………………………………………………… xiii  Summary ……………………………………………………………………………………………………………….. xv

CHAPTER ONE: INTRODUCTION ………………………………………………………………………….. 1

1.1 Background ………………………………………………………………………………………………………… 1

1.2 Problem Statement ………………………………………………………………………………………………. 5

1.3 Aim and Objectives ……………………………………………………………………………………………… 7

1.3.1 Aim………………………………………………………………………………………………………………….. 7

1.3.2 Objectives ………………………………………………………………………………………………………… 7

1.4 Justification for the Study ……………………………………………………………………………………… 7

CHAPTER TWO: LITERATURE REVIEW………………………………………………………………… 9

2.1 Nomenclature ……………………………………………………………………………………………………… 9

2.2 Historical Perspective …………………………………………………………………………………………. 12

2.3 Epidemiology of Asymptomatic bacteriuria in pregnancy………………………………………… 16

2.4 Pathophysiology of Asymptomatic bacteriuria in pregnancy……………………………………. 24

2.5 Organisms implicated in Asymptomatic bacteriuria in pregnancy………………………. 26

2.6 Risk factor for Asymptomatic bacteriuria in pregnancy…………………………………………… 27

2.7 Diagnosis of Asymptomatic bacteriuria in pregnancy……………………………………………… 28

2.7.1 Culture diagnosis……………………………………………………………………………………………… 29

2.7.2 Microscopic diagnosis ……………………………………………………………………………………… 30

2.7.3 Dipstick Urinalysis…………………………………………………………………………………………… 32

2.7.4 Other investigations available in diagnosis of asymptomatic bacteriuria…………………..38

2.8 Drug sensitivity and resistance studies ……………………………………………………………………39

2.9 Treatment of Asymptomatic bacteriuria…………………………………………………………………. 41

2.10 Cost effectiveness of Urinalysis vs Culture………………………………………………………….. 44

2.11 Prevention of recurrent Asymptomatic bacteriuria in pregnancy…………………………….. 46

2.12 Summary of Literature review……………………………………………………….…47

CHAPTER THREE: MATERIALS AND METHOD ………………………………………………….. 49

3.1 Study Area…………………………………………………………………………………………………………. 50

3.2 Study Population………………………………………………………………………………………………… 50

3.3 Study period………………………………………………………………………………………………………. 50

3.4 Study design………………………………………………………………………………………………………. 50

3.5 Sampling………………………………………………………………………………….50

3.5.1 Sample Size Estimation…………………………………………………………………50

3.5.2 Inclusion Criteria……………………………………………………………………….51

3.5.3 Exclusion Criteria………………………………………………………………………51

3.5.4 Sampling technique/ sampling interval…………………………………………………52

3.6 Study Protocol……………………………………………………………………………53

3.6.1 Instruments of data collection………………………………………………………….53

3.6.2 Administration of questionnaire………………………………………………………54

3.6.3 Physical Examination…………………………………………………………………..54

3.6.4 Sample collection………………………………………………………………………55

3.6.5 Dipstick Urinalysis…………..………………………………………………………….56

3.6.6 Urine culture……………………………………………………………………………57

3.7 Definition of terms……………………………………………………………………….59

3.8 Data entry and analysis……………………………………………………..…………….60

3.9 Ethical Considerations…………………………………………………………………………………………. 61  CHAPTER FOUR: RESULTS ………………………………………………………………………………….. 62

4.1 Subject Flow through the Study …………………………………………………………………………… 62

4.2 Baseline characteristics of participants at enrolment…………………………………………………64

4.3 Distribution of ASB by dipstick urinalysis and urine culture……………………………66

4.4 Results obtained from Dipstick urinalysis and urine culture………………………………………68

4.5 The prevalence of ASB using dipstick urinalysis and urine culture…………………………….69

4.6 Comparison of Dipstick Urinalysis versus Culture among participants……………………….70

4.7 Organisms implicated in ASB in the studied population……………………………………………71

4.8 Sensitivity, Specificity, Positive/Negative Predictive Values of the test…………………72

.

CHAPTER FIVE: DISCUSSION……………………………………………………………75

5.1 Prevalence of ASB in pregnancy…………………………………………………………75

5.2 Socio-demographic distribution and ASB…………………………………….………….76

  

5.2.1 Relationship between Age group and ASB………………………………….…………76

5.2.2 Marital status………..………………………………….………………………………77

5.2.3 Educational Status attained……………………………………………………………..77

5.2.4 Relationship between parity and ASB………………………..……………………….78

5.2.5 Relationship between gestational age and ASB…………………..……………………78

5.3 Factors associated with ASB in pregnancy………………………………………………79

5.3.1 Frequency of sexual intercourse in preceding week…….……..………………………79

5.3.2 Douching………………………………………………………………………….……79

5.4 Organisms isolated……………………………………………………………………….79

5.5 Performance of dipstick urinalysis detection of nitrites for ASB………………………..80

5.6 Relevance to General Medical Practice / Family Medicine………………………………81

5.7 Strengths of the Study ………………………………………………………………………………………… 82

5.8 Further research needs……………………………………………………………………83

5.9 Conclusion………………………………………………………………………………..84

5.10

Recommendations……………………………………………………………………….……..85

REFERENCES ………………………………………………………………………………………………………..86

APPENDICES ………………………………………………………………………………………………………..107

                                                            CHAPTER ONE:     INTRODUCTION

1.1        Background

Urinary tract infections (UTIs), which refer to both microbial colonization of the urine and tissue invasion of any structure of the urinary tract, are among the most commonly encountered infectious diseases by clinicians in developing countries. The estimated annual global incidence of UTI is at least 250 million.1 It affects all age groups and gender, but women are more susceptible than men, due to short urethra, absence of prostatic secretion, pregnancy and easy contamination of the urinary tract with faecal flora.1

Pregnant women are more susceptible to UTIs because of the numerous changes in the woman’s body caused by her pregnant state.1 Hormonal and mechanical changes increase the risk of urinary stasis and vesicoureteral reflux.2 These changes include ureteral dilatation, increased bladder volume, decreased bladder tone and decreased ureteral tone. These, along with an already short urethra (approximately 3-4 cm in females) and difficulty with hygiene due to a distended gravid uterus, increase the frequency of UTI in pregnant women.2 Development of glycosuria seen in 70% of such women also encourages bacterial growth in the urine. For these reasons, UTIs are among the most common bacterial infections during pregnancy.3

In general, pregnant women are considered immunocompromised UTI hosts because of the physiologic changes associated with pregnancy. These changes increase the risk of serious infectious complications from asymptomatic and symptomatic urinary infections even in healthy pregnant women.2

UTI may manifest as symptomatic bacteriuria (SB) or asymptomatic bacteriuria (ASB).4SB presents as burning with micturition (dysuria), urinary frequency, urinary urgency, and/or suprapubic pain. It is defined as more than 100 organisms per milliliter (/mL) of urine with accompanying pyuria (> 7 white blood cells [WBCs] /mL) in a symptomatic patient. Fever or costovertebral angle tenderness indicates upper urinary tract involvement.4

Asymptomatic bacteriuria or asymptomatic UTI refers to the persistent bacterial colonization of the urinary tract without clinical signs or symptoms of UTI in the host.4,5 The term ‘bacteriuria’ means the presence of bacteria in urine. It may result from contamination during or after collection of urine, or it may indicate the presence of bacteria in bladder urine.6 To distinguish among these possibilities; Kass introduced the term “significant bacteriuria” which was defined as the presence of at least 100,000 organisms per milliliter of voided midstream urine aseptically collected in an asymptomatic patient.6 Although the original criterion for diagnosing ASB was the presence of more than 100,000 bacteria/ml on two consecutive clean catch urine samples, a more practical alternative is the detection of more than 100,000 bacterial/ml in a single voided midstream urine sample.7

Asymptomatic bacteriuria has been previously reported to have an overall prevalence of 2-13% in pregnant women compared with that of symptomatic UTI which occurs in 1–18% of pregnancies.8,9 Prevalence of ASB in pregnancy however varies with the population. It is therefore important to evaluate the prevalence of ASB in specific populations.10

Pregnancy enhances the progression from asymptomatic to symptomatic bacteriuria which could lead to complications such as pyelonephritis, hypertensive disorders of pregnancy, anaemia, chronic renal failure and adverse obstetric outcomes such as prematurity, intrauterine growth retardation, low-birth-weight infants, and foetal mortality.11 In a review of trials on antibiotic treatment for pregnant women with ASB in which 14 studies involving 2302 women were reviewed, proper antibiotic treatment of ASB was found to be effective in reducing the incidence of pyelonephritis and low birth weight, but a difference in preterm delivery was not seen in those

trials.7

The American College of Obstetrics and Gynecology (ACOG) advocates routine screening for bacteriuria with a urine culture at the first prenatal visit and during the third trimester.12 The United States Preventive Services Task Force recommends screening for bacteriuria with urine culture for pregnant women at 12-16 weeks of gestation, hoping to identify 80% of women, who will eventually develop ASB. 13

A study carried out in Benin City, Nigeria suggested that routine urine culture test should be carried out on all antenatal women to detect asymptomatic bacteriuria and prevent the possible serious consequences for both the mother and the child.14

Approximately 1-2 % of women who are not bacteriuric at initial screening early in pregnancy will develop bacteriuria later in pregnancy.9 First trimester urine culture remains the screening test of choice, because reliance on symptoms to prompt screening is inadequate since the state of pregnancy can provoke frequency and nocturia.2

UTIs in women cost the United States of America approximately 3.5 billion dollars a year, making it one of the five most expensive urologic problems. This leads to more than 8.3 million physician office visits per year and more than 100,000 hospital admissions primarily for acute

pyelonephritis.15, 16

Screening for ASB in pregnant women has been shown to be cost effective when compared with treating UTI and pyelonephritis without screening.17 The effectiveness of screening for ASB depends on the availability of adequate diagnostic tools.8 The various screening techniques used to detect bacteriuria include urinalysis, leukocyte esterase activity, a nitrite test, microscopy and urine culture. A midstream urine culture is still considered the best diagnostic test or the gold standard.18

Due to the potential adverse sequelae of UTI in pregnancy, most clinics perform routine urinalysis of Mid-Stream Urine (MSU) specimen during one or more Antenatal Clinic (ANC)

visits.15

The most accurate test for bacteriuria is urine culture, but laboratory charges makes this test expensive for routine screening in populations that have a low prevalence of ASB.6 The decision about how to screen asymptomatic women for bacteriuria is dependent on the  balance between the cost of screening versus the sensitivity and specificity of each test. In addition, it takes 24-48

hours to obtain results.6

Difficulties in screening for ASB may arise at several different levels.9 First, the health care provider has to have increased awareness of the importance of ASB.9 Educational programmes that promote the availability of ANC and emphasize the importance of an early first antenatal visit (< 28 weeks of pregnancy) to the health centre are paramount to the successful implementation of this intervention.9 

The use of less expensive antibiotics, based on susceptibility testing, such as nitrofurantoin and those with potentially less side effects, will increase the likelihood of success in implementing

this intervention. However, the most effective length of treatment has not been determined.9

Poor maternal health is not only a consequence of lack of services but also the limited quality of care of existing services. Poor quality is often due to lack of resources, inadequate humane treatment, insufficient information exchange and lack of technical competence. Among the steps to be taken to decrease maternal mortality as given by the WHO/UNICEF/UNFPA, 2001 report,

is screening and treatment of asymptomatic bacteriuria.19

More information is needed about the prevalence of ASB in different populations, at different gestational ages, as well as the recurrence rates in those completing treatment. Further clarification of the importance of lower colony counts in urine culture, than those currently used

for diagnosis of ASB, and their association with pyelonephritis has to be explored.9

The diagnostic characteristics (sensitivity, specificity, etc) of screening tests for ASB, which could be equal or better in diagnostic accuracy than quantitative urine culture, but less expensive

or complex, is an area where research efforts should also focus on.9

Because ASB is clinically significant in pregnancy, it should be aggressively sought, diagnosed, and treated in all stages. Screening is an essential component of prenatal care.20

Dipstick urinalysis is readily available, easy to perform and a positive test, being highly suggestive of bacteriuria should enhance commencement of treatment, while awaiting results of

urine culture.20

1.2        Problem Statement

Urinary tract infection is the second most common clinical indication for empirical antimicrobial treatment in primary and secondary care, and urine samples constitute the largest single category of specimens examined in most medical microbiology laboratories.21 A Canadian and American study showed that approximately 50% of all women will have a UTI in their lifetimes, and 25% will have recurrent infections.22

Asymptomatic bacteriuria is common in pregnancy, a significant number of whom will develop symptomatic UTI during the course of the pregnancy.23 Untreated ASB leads to the development of symptomatic cystitis in approximately 30% of patients and can lead to the development of pyelonephritis in up to 50%.23

Pregnant women are at increased risk for bacteriuria due to certain physiologic factors associated with pregnancy.24 Approximately 90 percent of pregnant women develop ureteral dilatation, which will remain until delivery (hydronephrosis of pregnancy).24 Increased bladder volume and decreased bladder tone, along with decreased ureteric tone, contribute to increased urinary stasis and ureterovesical reflux.24 These factors may all contribute to the development of ASB and SB during pregnancy.

The adverse effects of undiagnosed ASB on the mother, and adverse obstetric outcomes which affects the child, have made researchers to suggest routine screening for all pregnant women attending ANC in order to prevent mother and child from any form of complication that may

arise due to infection.24

Urine culture is used as the reference standard to determine presence or absence of bacteriuria. However, culture is an expensive and time consuming method. Urine culture takes at least 48

hours to be obtained.25 In many developing countries, financial constraints may restrict the feasibility of introducing general screening of all pregnant women using the urine culture method.9

Most hospitals in developing countries including Nigeria do not carry out urine culture test routinely for antenatal patients to screen for ASB.9,14 This may probably be due to the cost implication and time factor for obtaining culture results (usually 48 hours period). Instead, many clinicians request for the strip urinalysis test to assess the urine for glucose and proteins, with the aim of screening for gestational diabetes and pre-eclampsia, giving little thought to the possibility of an asymptomatic bacteriuria in these women. 9,14  A urine test strip that will include nitrite and leukocyte esterase component can be of great help in screening for the ASB in such women.4

The diagnostic characteristics (sensitivity, specificity, etc) of screening tests for ASB, which could be equal or better in diagnostic accuracy than quantitative urine culture, but less expensive

or complex, is an area where research efforts should also focus on.9

1.3        Aim and Objectives

1.3.1 Aim

The aim of the study was to compare dipstick urinalysis with urine culture (gold standard) in the diagnosis of asymptomatic bacteriuria among booked pregnant women attending ANC in Plateau State Specialist Hospital Jos, Nigeria.

This was expected to establish whether the diagnosis of ASB in pregnancy by dipstick urinalysis was comparable to urine culture as a gold standard.

1.3.2 Specific Objectives

The specific objectives of the study are:

  1. To determine the prevalence of ASB among booked antenatal women in PSSH Jos using dipstick urinalysis and urine culture.
  2. To perform urine culture on the same urine samples and determine the organisms commonly implicated in ASB among booked antenatal women in PSSH Jos.
  3. To calculate the sensitivity, specificity, positive predictive value, negative predictive value and accuracy of dipstick urinalysis in detecting ASB, using urine culture as gold standard.

 

1.4        Justification for the Study

Family Medicine encourages the use of cost effective primary care and prevention strategies. While going through the Obstetrics and Gynaecology (O&G) posting as a resident, the researcher had course to participate in the management of some cases of pyelonephritis in pregnancy. He was also faced with the challenge of seeing booked antenatal care patients with their routine urinalysis result (which usually did not include leukocyte esterase) and deciding who should be treated for ASB or who will benefit from a culture request before treatment. Urine culture as a screening test for ASB in pregnancy was not a routine in the hospital. This may probably be due to its higher cost as compared to urinalysis since most of the women were of low socio-economic backgrounds. The researcher also observed that the attention of clinicians and health care providers was usually on the presence of glucose and protein in the urine specimens of these women, with less attention on possible asymptomatic infection. There was also lack of objective data on the correlation between the urinalysis results, and urine culture as a gold standard.

Dipstick urinalysis is easy to perform, requires less time and does not need highly trained personnel for the test. Any advance in the diagnosis and treatment of this entity could therefore have a major economic impact. Streamlining the diagnostic process will be of great help to the frontline physician in screening patients, making prompt diagnosis and providing adequate treatment. This will also decrease morbidity and improve patient outcomes and satisfaction.

Against this background, this work is aimed at comparing the use of dipstick urinalysis and urine culture in the diagnosis of symptomless UTI among booked pregnant women attending ANC in PSSH Jos. The study is also expected to add to the existing knowledge on the risk factors for developing ASB, in a Family Practice antenatal setting.

 

 

 

COMPARISON OF DIPSTICK URINALYSIS WITH URINE CULTURE IN THE DIAGNOSIS OF ASYMPTOMATIC BACTERIURIA AMONG PREGNANT WOMEN ATTENDING ANTENATAL CLINIC IN PLATEAU STATE SPECIALIST HOSPITAL, JOS

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