Non-gynae screening
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Introduction
Non-gynae screening test is an examination of a full range of cytology investigation that covers, "sputum and other respiratory specimens, urine, body cavity fluid and fine-needle aspiration cytology (FNAC) specimens" according to NGCS1. During the screening test, the specimens need to undergo standardized preparation methods as explained by Eindenet al.2 The test normally is conducted on request by patients and the duration of the investigation may vary depending on the specimen, the slide or the performing laboratory.
During the aspiration, a thin needle is inserted in the place with abnormal tissue or body fluid. This procedure is always considered safe with non-frequented complications, and like other biopsies, it can be used to detect or overrule cancer. FNA is commonly conducted on lymph nodes, cyst and nodules or masses. The samples drawn by the needle is then tested under a microscope in the laboratory, according to ASC.3(p5)
Different laboratories have formalized and documented procedures for labeling patients specimen and request forms. The procedures are well laid on from labeling, handling, the receipt and investigation of the specimens in order to ensure patient care safety and quality of procedure. The standards help ensure correct investigations are performed on the right specimen, and the results released are correctly identified and delivered to the right patients. The clinical notes contained within the forms are essential for the interpretation of the specimen test results.
According to Cibas and Ducatman4, “sensitivity and specificity of cytology testing varies depending on the sampling procedure employed and the location of sampling.” Combination of biopsies and cytology increase the detection rate in testing, with the correct interchange of the procedures. The strict quality control procedures followed ensure accuracy.
This screening was conducted with the aim of providing with the feedback and accuracy of the interpretation and final diagnosis. The tests are normally done within limited periods in the workstations. The project will aid in accomplishing the best learning process and equip with skills on screening cytopathology samples.
Methodology
In this project, the specimens covered are non – gynae specimens. The samples contain negative, benign, inconclusive, and malignant in non – gynae part only. This project is based on the evaluation of the quality assurance during three months of 147 cases provided by RMIT University (cytology department)5. The screening process was conducted on all different samples of non – gynae samples.
To achieve specific goals of a high percentage of quality in terms of performance of screener and results, the quality control and quality assurance must be used in cytology laboratories. Cytology lab should base on two potential types of quality, which are internal quality and external quality. The qualified employees are part of the quality assurance to achieve specific measurement. In addition, the laboratories equipment, precautions of safety and principle and procedure of the specimen preparation play an important role in quality as a general. The accreditation from high-quality level labs for example National Pathology Accreditation Advisory Council (NPAC)6 in Australia is necessary to have an international standard.
Internal quality is essential for measuring the quality performance of cytology screeners to achieve the specific level of accuracy of diagnosis in non – gynae cytology continuously. An assessment of the ability of a cytology screener depends on detecting the false negative standard, specificity and sensitivity. This equation (FNR = FN/(TP+FN)) is used to calculate the false negative which means TP is the true positive and FN is false negative, the abnormal Pap test measured proportionally. To measure false negative rate FNR, the false negative should be calculated. To measure the specificity and the sensitivity, the false positive and a false negative rate should be considered to achieve the accuracy. To measure the specificity this equation should be used as explained by Sukon7:
Specificity = TN/(FP+TN).
Hence, the sensitivity is measured by this equation:
Sensitivity = TP/(TP+FN).
The both previous equations can be used to detect the ability of the scientific cytology screeners and the documents reliability too.
Furthermore, it can use the equations to assess the positive predictive value PPV and negative predictive value NPV. Those parameters measure a specific part of accuracy that belongs to “undercalls” FPs and “overcalls” FNs by the cytology screener. Histological correlation is important to be followed to support the cytology result and increase the sensitivity of the test.
In this project, the accuracy will be measured in all results, and the false positive and false negative will be discussed and interpreted. In addition, the result of the histology correlation will include in this project.
Non- Gynaecological project that has 200 cases are previously diagnosed and doted carefully by cytology scientist. These cases were re-screened and compared with its histology correlation and provided in this report. Non – gynae specimens were from a different site of the body such as respiratory, effusion, urinary tract, and fine needle aspiration FNA. The terminology that has been used in this project is based on Betheseda Terminology system8 as following:
“Unsatisfactory”: the reason is included.
“No Abnormality Detected NAD”: either due to infection or normal entities.
“Benign”: normal entities without harm impact.
“Inconclusive”: with comment.
“Suspicious”:
“Malignant”: the type of abnormality is detected.
In the other hand, thyroid FNA specimens are recorded based on Bethesda Reporting System of Thyroid FNA.
The Non – gynae specimens were screened and checked under Olympus light microscope in two days of the week Monday and Thursday from 9:00 am to 4:30 for 11 weeks. All cases classified in tables. The results checked by the course coordinator to confirm the result or to correct them.
Data Analysis and Presentation
Fig. 1: Pie chart representing specimen types screened.
Fig. 2: Chart showing the percentage representation of the results obtained.
Fig. 3: Bar graph indicating the results obtained and the number of specimens
Fig. 4: Graph showing sensitivity of the test conducted.
Statistical Analysis
Sensitivity = TP/(TP+FN)
= 83/(83+9)
=83/92
=0.902
Specificity = TN/(FP+TN)
=28/(17+28)
=28/45
=0.6222
Prevalence = (TP+FN)/(TP+TN+FP+FN)
= (83+9)/(83+28+17+9)
= 92/ 137
=0.67
PPV (Positive Predictive Value) = TP/(TP+FP)
= 83/(83+17)
= 83/100
= 0.83
NPV (Negative Predictive Value) = TN/(FN+TN)
= 28/ (28+9)
= 28/37
= 0.7568
Results and Discussion
Lab results can be positive, negative or even inconclusive9. As it can be observed in figure two, it is expressed the extent in which the results were obtained. In figure four, out of the 147 screening that were carried out, 83 of the tests proved positive. This means that the conditions diagnosed and that were screened for were actually proved to be. The substance being tested for can be found to be high or lower than the normal level, or to some extent non-disruptive.
In figure 2, there are results that raised suspicion, others that were not satisfactory and the others that were inconclusive. These tests never clearly gave positive results hence could be disputed. Such results are said to be inconclusive since no concrete solution can be made from them. The tests that raised suspicion cannot be taken to be conclusive, specimen have to be obtained again, and the test be conducted. In the tests whose results are inconclusive, conclusion cannot be drawn from the test results whether the test can be confirmed or disapproved.10
From the graphs and charts, it can be seen that there were negative results too. The test did not confirm all the potentialities being investigated in all the specimens. A negative result is achieved where a condition being investigated is not confirmed nor found. The results being tested for can also be found to be present in abnormal form in the specimen. This can also be declared negative.
According to Brown11, the test result is positive if the condition tested for is present. This can also be said to be true positive. If the results indicate that the condition tested for is present while it is not present if a rescreening or a confirmatory test is performed, then it is a false positive. A test may give results that a person has a condition or a disease being tested for a while in actual sense it is not present. As seen in figure four, 17 of the specimen being screened for tested positive while in the actual sense they were negative.
A test on the other hand may not test for the condition being investigated even though it is present. Such test is a false negative. A false negative may suggest that a patient is free from the condition or disease being tested for when in reality the disease or the condition is present12. After a doctor’s diagnosis of the condition and requesting for a test to be conducted on a patient, the negative test may provide a misleading result that may limit the treatment offered to the patient. As in figure four, a false negative was obtained in nine specimens.
Sensitivity is the ability of a test design to test for the disease or condition being investigated correctly through defined criteria7. Even though there is increased accuracy in the manner in which tests are conducted, there are still chances of errors detected. There are some disease and conditions that must always be subjected to confirmatory testing in order to confirm, while others, there are several number of slides subjected to testing.
The number of slides for same test increases sensitivity as there is consistency that is provided to ascertain that the results detected are real. If there is inconsistency in the number of slides being tested for the same condition or disease, then that is a clear indication of reduced or lack of sensitivity of the test kits. From the results here, the sensitivity of the test was high at 0.902 confirming that the investigation could test for the conditions being screened for.
Quality of strain aids in the test investigating to identify correctly the disease being tested. Poor quality strains will compromise the ability of the test to confirm the condition being investigated. A high sensitivity in the test will remove any doubt in the results obtained and helps rule out a disease if an investigation tests negative7.
The challenges encountered during the test were that the limited time while screening presented with the impact is rushing led to missing some cells and tests. The time that should be spent on Pap smear either liquid base or conventional or cytospin smear differ according to the laboratory where the test is conducted. It can take up to a week or two for an individual to obtain results. Lack of experience may impact the investigation process in the laboratory in different ways. Lack of knowledge in non – gynae specimens during the screening led to a decrease in sensitivity.
Conclusion
This test was carried out on specimen that werenongenealogical so as to establish the presence of diseases or conditions in them. All the laid down procedures and laboratory requirements for non-gynae screening was put into consideration. Some specimens were liquid based extracted through FNA while others were tissues extracted by scrapping. All the standard time required to screen the specimen was taken into consideration so as to ensure quality4.
The test had higher of sensitivity at 0.902 though the specificity was low at 0.6222. This means that the test had a higher degree of overruling a disease existence by providing true positives more than it will on ruling out the absence of disease from a person by providing true negatives. From the tests, the unsatisfactory, inconclusive and suspicious results identified were very few at 6%, 3% and 2% respectively of the total specimen screened.
The screening confirmed that the method can be comprehensively used for investigating specimen on disease and conditions since it provided for a high level of sensitivity. The strains quality was also high possible enough to give the desired level of sensitivity and conclusive results from the screening test according to Sukon7.
References
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3. American Society of Cytopathology (ASC). (2004) Non-gynecological Cytology Practice Guideline. Retrieved from http://www.cytopathology.org/wp-content/dynamic_uploads/54.pdf
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11. Brown, S. Medical False Positives and False Negatives. New York: Tompkins Cortland Community College; 2013. Retrieved from http://www.tc3.edu/instruct/sbrown/stat/falsepos.htm
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