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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 14  |  Issue : 2  |  Page : 88-91

Determination of the sensitivity and specificity of serum prostate-specific antigen in the diagnosis of prostrate cancer in Kano, Northwestern Nigeria


Department of Surgery, Bayero University/Aminu Kano Teaching Hospital, Kano, Nigeria

Date of Web Publication5-Oct-2017

Correspondence Address:
Sani A Aji
Department of Surgery, Bayero University/Aminu Kano Teaching Hospital, Kano
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njbcs.njbcs_39_16

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  Abstract 

Background: Early detection is an essential step in decreasing the mortality and morbidity related to prostate cancer. Serum prostate-specific antigen (PSA) testing is a proven effective tool for early detection of prostate cancer. It has high sensitivity but low specificity and remains an important screening tool. Objectives: This study aims at finding a local reference sensitivity and specificity level of serum PSA in Kano, Northwestern Nigeria. Materials and Methods: A cross-sectional descriptive study of 93 patients who had lower urinary tract symptoms and digital rectal examination (DRE) findings suggestive of cancer of the prostate and/or raised PSA who presented to urology outpatient clinic of Aminu Kano Teaching Hospital, Kano over the period of one year (January to December 2012). All patients had transrectal ultrasound-guided biopsy for histological evaluation. The sensitivity and specificity of PSA were then analysed. Results: A total of 93 patients participated in the study with age range from 50 to 96 years and mean age of 68.086 ± 9.368 years. The sensitivity of PSA was found to be 91.4% but dropped to 47.3 when the reference ranged were considered at 0–4.0 ng/ml and 0–10.0 ng/ml, respectively. Also, the specificity was found to be 22.4% but raised to 77.0% at the other reference range. The diagnostic accuracies for 0–4 and 4.1–10 ng/ml were 48.0% and 59.1%, respectively. Conclusions: PSA testing still has a role to play in the diagnostic pathway and is relatively non-invasive, inexpensive with a high sensitivity. However, it has a low specificity. The reference range in our environment remains the international range of 0–4 ng/ml.

Keywords: Prostate cancer, sensitivity, serum total PSA, specificity


How to cite this article:
Yunusa B, Abdullahi M, Mashi SA, Aji SA, Alhassan SU. Determination of the sensitivity and specificity of serum prostate-specific antigen in the diagnosis of prostrate cancer in Kano, Northwestern Nigeria. Niger J Basic Clin Sci 2017;14:88-91

How to cite this URL:
Yunusa B, Abdullahi M, Mashi SA, Aji SA, Alhassan SU. Determination of the sensitivity and specificity of serum prostate-specific antigen in the diagnosis of prostrate cancer in Kano, Northwestern Nigeria. Niger J Basic Clin Sci [serial online] 2017 [cited 2017 Oct 21];14:88-91. Available from: http://www.njbcs.net/text.asp?2017/14/2/88/216050


  Introduction Top


Prostate cancer is the most common male cancer and the fourth most common cancer in the United Kingdom (UK), comprising 24.1% of all cancers in men. Nearly 32000 men are diagnosed in the UK each year, out of which 9000 will die of the disease.[1]

It is also the most common cause of cancer in European men and third most common cause of death worldwide. The incidence is rising [2] even among the Africans and is now the leading cancer either due to race or increase in our diagnostic methods.[3],[4] It is the most common male cancer in Nigeria.[5]

Detection of prostate cancer relies on an abnormal digital rectal examination (DRE) and/or increased prostate-specific antigen (PSA) levels. Despite its widespread use, PSA has marginal specificity, and 65–70% males with elevated PSA levels within 4–10 ng/ml and this has led to unnecessary negative biopsy result.[6]

To improve PSA specificity, various parameters have been introduced. These include PSA density, PSA velocity, and free/total PSA; however, these methods have not appreciably improved the cancer detection rates. In addition, because of sampling errors or sampling inefficiencies associated with transrectal ultrasound-guided biopsy of the prostate, some prostate cancer may be missed (false negative).[6]

There is an increase in detection of early (curable stage) prostate cancer due to widespread use of PSA and multiple core biopsy protocol, leading to decrease in mortality.[7],[8]

Serum PSA, also known as human kallikrein 2, is produced by the luminal prostatic cells, which line the prostatic acini. It is responsible for liquefying semen and hence has a major role in fertility. It is possible to detect PSA in small amounts in the serum of healthy males and this level increases in prostate cancer. However, while PSA is tissue specific an increase in circulating levels is not definitively linked to tumour development. Urethral instrumentation, urinary infection, prostatitis, urinary retention, ejaculation, and benign prostatic hypertrophy all raise serum PSA levels.[1]

We planned to find the sensitivity and specificity of PSA in our environment so as to have a local reference parameter as regard to cancer of the prostate, having known it to be an important public health issue in sub-Saharan Africa.

This study aims at determining a local reference for the sensitivity and specificity level of serum PSA in Kano, Northwestern Nigeria.


  Materials and Methods Top


This is a prospective descriptive cross-sectional study involving 93 consecutive patients with lower urinary tract symptoms, DRE findings suggestive of cancer of the prostate and/or raised PSA more than 4 ng/ml who presented to our outpatient clinic over the period of one year (January to December 2012) and also consented to be enrolled.

These patients were subjected to transrectal ultrasound scanning complimented with Doppler to identify any suspicious lesion and biopsied, those without suspicious lesions had the traditional sextant biopsy. The sensitivity and specificity of the PSA was then analyzed and presented.

Total serum PSA of all the patients was determined using the electrochemical luminescent (ECLIA), on the elecsys 2010 automated analyzer. Quality control samples were included in each batch. Transrectal ultrasound-guided biopsy was carried out on all the patients for histological evaluation.

Ethical approval was obtained from the Ethics committee of Aminu Kano Teaching Hospital, Kano before the study was commenced.


  Results Top


There were 93 respondents recruited for the study out of 110, thus giving a response rate of 84.5%. The remaining 17 (15.5%) defaulted after screening DRE and PSA determination.

The age of the participants ranges from 50 to 96 years with mean of 68 ± 9.368 as shown in [Table 1].
Table 1: Sociodemographic characteristics of the respondents

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[Table 2] shows the occupational distribution of the patients with majority of them (36.56%) being businessmen.
Table 2: Occupational distribution of the respondents

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Using the cut-off point of 0–4 ng/ml as normal, the sensitivity of PSA was found to be 91.4%, with a specificity of 22.4%, and an accuracy of 48% [Table 3].
Table 3: Showing the Sensitivity and specificity of PSA using conventional 0-4 ng/ml as cut-off of normal

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Using the cut off of 0–10 ng/ml, the sensitivity of PSA was found to be 47.3%, specificity of 77% with an accuracy of 59.1% [Table 4]. With a statistically significant difference at x 2 = 16 and P = 0.0001.
Table 4: Shows the sensitivity and specificity of PSA using the gray zone of 4-10 ng/ml as part of the normal values

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  Discussion Top


Prostate cancer is the most commonly diagnosed malignancy among men, and the peak incidence is in the sixth to seventh decades of life. The disease has a profound emotional and functional effect on patients and their caregivers and imposes a large financial burden.[9]

Relatively little is known about the epidemiology of prostate cancer in men in Sub-Saharan Africa (SSA), however it is clear that men of SSA descent around the world suffer disproportionately from this type of cancer.[10] It is the leading cancer in terms of incidence and mortality in Africa, as well as a growing problem in Africa. Despite the importance of this public health issue in SSA, there remains relatively limited information about practices related to prostate cancer in this population, so the need for us to make available information and screening tools and to encourage people to screen. It is well known that screening leads to early detection thereby reducing morbidity and mortality.

The incidence in Nigeria (127/100,000) is comparable to that in African American men, with an annual death rate of about 20,000. With the increasing life expectancy in Nigeria, more men will be diagnosed with prostate cancer.[9],[11],[12]

Serum PSA values have some limitations for early detection of prostate cancer, despite that, it remains the best test for early detection,[13],[14] and has been used for diagnosis, follow up of treatment, and screening the disease. Serum PSA, produced mainly by the prostatic epithelial cells and the periurethral glands, can be found in various body fluids.[12]

We found that the age of the respondents in our study ranged between sixth and tenth decades, with a mean of 68 ± 9.4 years in keeping with the age where most prostate cancers are diagnosed.[9] Seventy-seven per cent of the respondents fall within the age limits of 60 to 89 years with less than 15% in the age below 60 years. Thirty-seven percent of the responders are business men while twenty-seven percent are pensioners. [Table 2] shows the distribution by occupation. To our knowledge, a relationship has not been established between these occupations and cancer of the prostate.

[Table 3] shows the sensitivity of the PSA at 0–4 ng/ml cut off to be high about 91.4% in keeping with some findings of 91.7%.[13] Sensitivity is defined as the ability of a test to detect the actual positive, and for a screening test to have high sensitivity; it will pick a lot of false positive subjecting patients to unnecessary biopsy with its attendant complications and the psychological morbidity. But at the same time, it has the potential advantage of early detection to identify patients with clinically significant disease that have biologic potential to cause morbidity.[8] While if the grey zone of 4–10 ng/ml is added within the normal range, as shown in [Table 4], the sensitivity will reduce to 47.3%, meaning it will have much false negative, and may miss a lot of early malignancies allowing it to reach advanced stage before detection, which will contribute to high mortality.

Overall serum total PSA seems to have great significance as a diagnostic tool. PSA test has value. Adequate levels of sensitivity appear to be achieved at the expense of poor specificity, with consequently relatively high numbers of false positive results.

The populations of our studies were limited to men attending urology clinics who were referred on account of high PSA, LUTS or an abnormal finding on DRE. This means that our results cannot be applied to the screening population. In this setting, there would be a lower prevalence of prostate cancer so it is likely that PSA would have less accuracy as a diagnostic test since the specificity has been shown to be low.

We have found that the PSA test had a sensitivity ranging from 47.3–91.7%, which means it potentially fails to diagnose over 10% of prostate cancers. This is important to consider in patients with continuing symptoms or an isolated, abnormal DRE. Good quality counselling and information needs to be given to patients to ensure they present again if symptoms persist or worsen. The DRE needs to remain a key part in the diagnostic pathway.

Specificity of a test is its ability to detect actual negative. [Table 3] shows the specificity to be 22.4% within 0–4 ng/ml as normal range, which is low, meaning the test will detect a lot of false negative, missing what may be biologically potential tumour-causing high morbidity and or mortality. [Table 4] shows a significant raise in specificity to 77% when 0–10 ng/ml is considered, in which the false negative will be much higher.

PSA is known to have low specificity; however, our results showed an extremely low range of 22.4–77%. All but Unal 2000 showed a specificity of less than 0.40.[1] This is in contrast to a moderate specificity as stated by the National Institute of Clinical Excellence (NICE) in the most recent guidelines on referral practice for suspected cancer in adults and children. Such a low specificity means that in practice many patients are undergoing the invasive procedure of biopsy who do not in fact have prostate cancer. However, there is currently no alternative that has been recommended by NICE for use in clinical practice.[1]


  Conclusion Top


Cancer of the prostate is a common male cancer globally and total serum PSA remains the best single test for early detection of prostate cancer because of its high sensitivity of about 91.4% but has a low specificity making it an unreliable marker in the absence of other indices that improve its specificity in our environment.

PSA testing still has a role to play in the diagnostic pathway and is relatively noninvasive and inexpensive. However, it has a low specificity. Other tests, which could improve this, are not widely implemented in our clinical practice. We recommend that PSA testing at the range of 0–4 ng/ml continues to be used in clinical practice as one of the several indicators for biopsy, but it is important that clinicians understand the limitations of the test.

It would be interesting to assess the role of a PSA result in physicians' decision making; for example, the impact of the high false positive and significant false negative rates. It might be interesting to sub-analyze the data according to the patients' presenting symptoms, as this would be useful in the assessment of PSA as both a diagnostic test and a screening tool.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Burden HP, Davis CR, Tate S, Persad R, Holmes CH, Whittington K. The trends in prostate specific antigen usage amongst United Kingdom urologists – A questionnaire based study. BMC Urol 2008;8:17.  Back to cited text no. 1
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Harvey P, Basuita A, Endersby D, Curtis B, Iacovidou A, Walker M. A systematic review of the diagnostic accuracy of prostate specific antigen. BMC Urol 2009;9:14.  Back to cited text no. 2
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Oranusi CK, Mbieri UT, Oranusi IO, Nwofor AME. Prostate cancer awareness and screening among male public servants in Anambra State, Nigeria. Afr J Urol 2012;18:72-4.  Back to cited text no. 3
    
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Rebbeck TR, Zeigler-Johnson CM, Heyns CF, Gueye SM. Prostate Cancer Screening, Detection and Treatment Practices Among Sub-Saharan African Urologists. Afr J Urol 2011;17:85-91.  Back to cited text no. 4
    
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Ebuehi OM, Otumu IU. Prostate Screening Practices Among Male Staff of the University of Lagos, Lagos, Nigeria. Afr J Urol 2011;17:122-34.  Back to cited text no. 5
    
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Nakai Y, Anai S, Kuwada M, Miyake M, Chihara Y, Tanaka N. et al. Photodynamic diagnosis of shed prostate cancer cells in voided urine treated with 5-aminolevulinic acid. BMC Urol 2014;14:59.  Back to cited text no. 6
    
7.
Yashi M, Mizuno T, Yuki H, Masuda A, Kambara T, Betsunoh H, et al. Prostate volume and biopsy tumor length are significant predictors for classical and redefined insignificant cancer on prostatectomy specimens in Japanese men with favourable pathologic features on biopsy. BMC Urol 2014;14:43.  Back to cited text no. 7
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El-Nahas AR, Abol-Enein H, Abdel-khalek M, El-Assmy A, Al-Kohlany K, El-baz M. A Rationale for Prostate Cancer Detection in A Developing Country: Comparison of screening and Case Finding. Afr J Urol 2003;9:123-8.  Back to cited text no. 8
    
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Ali M. clinical presentation, pathological pattern and treatment options of prostate cancer at Al- Azhar University hospital over the last 30 years. Afr J Urol 2001;17:135-40.  Back to cited text no. 9
    
10.
Mosli HA, Abdel-Meguid TA. The Relationship Between Prostate Volume, Prostate- Specific Antigen and Age in Saudi Men with Benign Prostatic Conditions. Afr J Urol 2010;16:117-23.  Back to cited text no. 10
    
11.
Okolo CA, Akinosun OM, Shittu OB, Olapade-Olaopa LI, Akang EE, et al. Correlation of serum PSA and gleason score in Nigerian men with prostate cancer. Afr J Urol 2008;14:15-22.  Back to cited text no. 11
    
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Heyns CF. Is Prostate Cancer more common and aggressive in Africa? Afr J Urol 2008;14:66-7.  Back to cited text no. 12
    
13.
Waldie BS, Abdelfatah ESA, Emara SE, Bazeed MA. The discriminative ability of percent free PSA in patients with PSA>10ng/ml. Afr J Urol 2005;9:24-7.  Back to cited text no. 13
    
14.
Sağlam HS, Köse O, Özdemir F, Adsan O. Do the values of prostate specific antigen obtained from fresh and dried urine reflect the serum measurements? Urol Ann 2013;2:99-102.  Back to cited text no. 14
    



 
 
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  [Table 1], [Table 2], [Table 3], [Table 4]



 

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