Statistical quality control in cervical-vaginal cythology: ASC-US/SIL Ratio.

Introduction Uterine cervix cancer is the second most common neoplasm in women. Of all uterine cervix and vagina cytologies, between 0,5 and 0,6% reveal high-grade squamous intraepithelial lesion (HSIL), and between 2 and 3% are low-grade squamous intraepithelial lesions (LSIL). The tem ASC-US (atypical squamous cells, of undetermined significance) is a diagnostic category, not a biological entity, that comprises inflammatory, reactive and reparative processes. In our revision of the literature, we found that ASC-US diagnosis comprises between 1,6 and 9% of the diagnosis, with an average around 5%. Other authors have employed with success the use of a ration between ASC-US and SIL as statistical quality control tool, whose value should not surpass 3,0.

Research methods It's a descriptive, retrospective study, based on the total of cervico- vaginal cytologies processed and diagnosed in this lab, since opening on July 1st, 2008 until December 31st, 2015.

Results We found a total of 58,289 cervico-vaginal exfoliative cytologies. From which 974 were diagnosed as ASC-US and 925 as SIL. The ASC-US/SIL ratio was, on average 1,16, with a standard deviation of 0,31. The range of the ASC-US/SIL ratio was between 0,69 and 1,67. The ASC-US diagnoses represented 1,67%, whereas the SIL diagnosis were 1,59% of all cases. ASC-US had an average of 2,06%, with a standard deviation of 0,99%, in a range between 0,67 and 4,09%. SIL had an average of 1,79%, with a standard deviation of 0,68%, in a range between 0,69 and 2,79%.

Discussion We found yearly variations of ASC-US/SIL ratio, that we attribute to human factors such as work load. In 2010, ASC-US/SIL ratio was set below one standard deviation from average, and in 2012 it was set above one standard deviation from average. Our ASC- US and SIL percentages were well below figures found in bibliographical references. Both figures also showed yearly variations. There was overdiagnosis of ASC-US in 2008, and of SIL in 2008 and 2010.

Conclusion To the extent of what we've been able to investigate, this is the first article about statistical quality control for uterine cervix and vagina cytology in Panama. Nevertheless, we still believe it is important to compare our findings with other labs willing to publish their results, to determine is ours constitute the statistical rule of the region or if they are an statistical annomay, favorable or disfavorable.

Introduction

In 1886, Sir John Williams found non-invasive abnormal epithelium adyacent to cervical squamous cell carcinoma. These findings were later and better described by Cullen in 1900. In the 1930's decade, Broders introduced the term carcinoma in situ to describe intraepithelial squamous lesions. Gavin, Jones and Telinde found a temporal relation between the diagnosis of carcinoma in situ and invasive carcinoma, proving their hypothesis that the first progressed to the later

The spectrum of lesions with cellular atypia that comprissed then the diagnosis of carcinoma in situ was so wide, that the term dysplasia was used to designate those less atypical that carcinoma in situ.(1)

George Papanicolaou introduced the uterine cervix and vagina cythology in 1943. Since then, there have been many classifications formulated The Bethesda System was designed to reflect the clinical and biological behavior of squamous intraepithelial neoplasia of the uterine cervix and vagina.(2-6)

At present time, cancer of the uterine cervix is the second most common neoplasm in women. Of all uterine cervix and vagina cithology, between 0,5 and 0,6% reveal high-grade intraepithelial lesion (HSIL), between 2 and 3% are low-grade intraepithelial lesion (LSIL).(3,7,8)

Both diagnosis of squamous intraepitelial lesion are defined by sexually transmited infection of human papilloma virus, high and low risk respectively. It's diagnosis has an established management in North America and Europe. Nevertheles, there is no established management for ASC-US diagnosis, a category that still causes uncertainty and confussion among clinicians and patients, mainly for it's clinical significance.(2,3,9)

The term ASC-US (atypical squamous cells, of undetermined significance), it's a diagnostic category, not a biological entity, that comprises inflammatory, reactive or reparative processes with insufficient cell atypia to be considered as squamous intraepithelial lesions (SIL) or cervical intraepithelial neoplasia (CIN). In our revision of the literature we found that the diagnosis of ASC-US ranges from 1,6 and 9% of the diagnosis, with an average around 5%.

(2,7,10,11,12)

Most experts recommend that this diagnosis should not exceed two or three simes the percentage of cases with LSIL diagnosis.(7) Other authors have employed with success the use of a ration between ASC-US and SIL as statistical quality control tool, whose value should not surpass 3,0.(11)

The higher the relation, the higher the uncertainty, whereas a lower ratio is interpreted as a higher diagnostic certainty of the lab, the cytotechnologist or the cytopathologist in question.

(11,13,14)

In a previous study done in this lab, the ASC-US/SIL ratio was 0,92. Nevertheless, most of the literature references studies with cytopathologist and cytotechnologist, not general pathologists.(12-15)

Research methods

Our main interest is to value the percentage of ASC-US and the ASC-US/SIL ratio in the course of the operations of this lab during 90 months, and to determine is there are year to year variations, product of human error.

Our hypothesis is that in average we will be within the range described by the literature for ASC-US as well for ASC-US/SIL.

It's a descriptive, retrospective study, based on the total of cervico-vaginal cytologies processed and diagnosed in this lab, since opening on July 1st, 2008 until December 31st, 2015. All diagnosis were made in conventional preparations stained with hematoxiline, orange G and EA50.

All the ASC-US. LSIL and HSIL results were tabulated. Unsatisfactory and with other diagnoses were included when adding the total cytologies to calculate percentages. Cases rejected for cytology processing were excluded for being innadequate.

Data was tabulated in OpenOffice 3.4.1 spreadsheets, with license of 2014 of Apache Software Foundation, the same program used to calculate the total of cases, the ASC-US/SIL ratio, the average, the standar deviation, the minimum value and the maximum value.

Results

Data is presented as follows:

Table 1: Absolute frequency of cervico-vaginal cytologies.

Table 2: Absolute frequency of atypical squamous cell, of undetermined significance (ASC- US) and squamous intraepithelial lesion (SIL), and ASC-US/SIL ratio.

Table 3: Average, standard deviation, ± 1 standard deviation range, minimum value and

maximum value of absolute frequency of atypical squamous cells, of undetermined significance (ASC-US), squamous intraepithelial lesion (SIL), and ASC-US/SIL ratio.

Table 4: Percentage of atypical squamous cells, of undetermined significance (ASC-US) and squamous intraepitelial lesion (SIL).

Table 5: Average, standard deviation, ± 1 standard deviation range, minimum value and maximum value of percentages of atypical squamous cells, of undetermined significance (ASC-US), and squamous intraepithelial lesion (SIL).

Discussion

What's most evident are the annual variations of the ASC-US/SIL ratio, that we ascribe to human factos such as work load

What's next most relevant in our descriptive data are the year 2010, in which the ASC-US/SIL ratio is set below one standard deviation from average, and 2012, in which the ASC-US/SIL ratio is set above one standard deviation from average.

The ASC-US/SIL ratio was of 1,16 ± 0,31, which establishes a range between 0,84 and 1,47 for our lab, with minimum value of 0,69 and maximum value of 1,67. These values are well below the maximum limit found in literature (3,0).

Next in relevance is our interest to know the percentage of ASC-US, 1,67%, and SIL, 1,59%. Both figures are below those found in the bibliographic references to our disposal.(2,7,10,11,12)

This finding was also subject to variations through time, finding an average and standard deviation for ASC-US of 2,06 ± 0,99% and for SIL of 1,79 ± 0,68%. This is why our range for ASC-US is set between 1,07 and 3,05%, and for SIL between 1,10 and 2,47%.

The same as found with the ASC-US/SIL ratio, there were years with percentages outside the calculated range. In both categories, ASC-US and SIL, 2015 was the year with the lowest percentages in both cases, while in 2008 there was registered an over-diagnosis of ASC-US, with 4,09%, and in the years 2008 and 2010 there was an over-diagnosis of SIL, with 2,79& and 2,63%, respectively, based in our statistics.

Conclusion

Conventional preparation of exfoliative uterne cervix and vagina cytology is still an effective tool with respect to cost, of equal sensibility and specificity as liquid based preparations, for detection of squamous intraepithelial lesions, mainly high grade.(16,17)

Once percentages os atypical squamous cells, of undetermined significance (ASC-US), squamous intraepithelial lesion (SIL), and ASC-US/SIL ratio were calculated, it's easier to appreciate the collective tendency of our lab, and re-evauate which diagnosis category we have been over-diagnosing or under-diagnosing.

It was a surprise to find that our results were lower than so many others found in literature of well-developed countries.(2,7,10-13)

To where we have been able to investigate, this is the first article on statistical quality control for cytology of uterine cervix and vagina in Panama. Nevertheless, we still believe it is important to compare our findings with other labs willing to publish their results, to determine is ours constitute the statistical rule of the region or if they are an statistical annomay, favorable or disfavorable.

We still have to investigate the patients found in our series, to determine which were the findings of cytological or biopsy follow-ups, as well as to determine the use of detection and typification of human papilloma virus, infectious agent that causes the hughe majority of pre- malignant lesions of uterine cervix and vagina.(1,4-6,16,17)

We are left with the doubt about the distribution by age group of all SIL and ASC-US, a subject that we have to investigate more deeply.

Bibliographical references

• 1. Kurman RJ, Hendrick Ellenson L and Ronnett BR (eds) Blaunstein's Pathology of the female genital tract Volume 1. 7th ed. Argentina: Amolca; 2014.

• 2. Macedo Barcels AC, Jorge Adad A, Antoniazi Michelin M and Candido Murta EF Atypical squamous cells of undetermined significance: Analysis of microbiology, cytological criteria and clinical conduct. Tumori 2006; 92: 213-218

• 3. Schiffman M and Solomon D. Finding to date from the ASCUS-LSIL triage study (ALTS). Arch Pathol Lab Med 2003; 127: 946-949

• 4. Carvalho G. Female genital tract cytology: the first step to stop uterine cervix cancer. 5th ed. Venezuela: Amolca; 2010.

• 5. Rosai J. Rosai and Ackerman's Surgical Pathology. 10th ed. Venezuela: Amolca; 2013.

• 6. Dallenbach-Hellweg G, Knebel Doeberitz MV and Trunk MJ. Color atlas of histopathology of the cervix uteri. 2nd ed. Buenos Aires: Ediciones Journal; 2006.

• 7. Schiffman M and Solomon D. Findings to date from the ASCUS-LSIL triage study (ALTS). Arch Pathol Lab Med 2003; 127: 946-949.

• 8. Davey DD, Neal MH, Wilbur DC, Colgan TJ, Styer PE and Mody DR. Bethesda 2001 implementarion and reporting rates: 2003 practices of participans in the College of American Pathologists Interlaboratory Comparison Program in Cervicovaginal Cytology. Arch Pathol Lab Med. 2004; 128: 1224-1229.

• 9. Stoler MH, Wright Jr TC, Sharma A, Apple R, Gutekunst K, Wright TL and ATHENA HPV Study Group. High-risk human papillomavirus testing in women with ASC-US cytology. Am J Clin Patho 2011; 135: 468-475.

• 10. Tworek JA, Jones BA, Raab S, Clary KM and Walsh MK. The value of monitoring human papillomavirus DNA results for Papanicolaou tests diagnosed as atypical squamous cells of undetermined significance. Arch Pathol Lab Med. 2007; 131: 1525- 1531.

• 11. Renshaw AA, Genest DR and Cibus ES. Should atypical squamous cells of undetermined significance (ASCUS) be subcategorized? Am J Clin Pathol 2001; 116: 692-695.

• 12. Alvarado Anchisi R, Espinosa C and Otero Martínez JJ. Atypical squamous cells in indigenous women resident of the Ngobe-Bugle region, republic of Panama, 2009- 2010. Rev Med Cient 2010; 23(2): 3-11.

• 13. Renshaw AA, Deschenes M and Auger M. ASC/SIL RATIO for cytotechnologists: a surrogate marker for sceening sensitivity. Am J Clin Pathol 2009; 131: 776-781.

• 14. Cibas ES, Zou KH, Crum CP and Kuo F. Using the rate of positive high-risk HPV test results for ASC-US together with the ASC-US/SIL ratio in evaluating the performance of cytopathologists. Am J Clin Pathol 2008; 129: 97-101.

• 15. Wachtel MS and Dahm PF. The ASCUS:SIL ratio and the reference laboratory pathologist. Cytopathology 2003; 14: 249-256.

• 16. Raab SS, Jones BA, Souers R and Tworek JA. The effect of continuous monitoring of cytologic-histologic correlation data on cervical cancer screening performance. Arch Pathol Lab Med. 2008; 132: 16-22.

• 17. Arbyn M, Bergeron C, Klinkhamer P, Martin-Hirsch P, Siebers AG and Bulten J. Liquid compared with conventional cervical cytology: a systematic review and meta-analysis. Obstet Gynecol 2008; 111: 167-177.

Appendices

Figure 1: Negative for intraepithelial squamous lesion or malignacy. Bright field, hematoxilin, EA50 and orange G stain, 400X.

Figure 2: Atypical squamous cells, of undetermined significance. Bright field, hematoxilin, EA50 and orange G stain, 400X.

Figure 3: Atypical squamous cells, of undetermined significance.
Bright field, hematoxilin, EA50 and orange G stain, 400X.

Figure 4: High-grade squamous intraepithelial lesion. Bright field, hematoxilin, EA50 and orange G stain, 400X.

Figura 5: Squamous cell carcinoma. Bright field, hematoxilin,
EA50 and orange G stain, 400X.

Authors:

R. Alvarado Anchisi,

Pathologist.

Y. González Araúz,

Medical technologist – cytotechnologist.

I. Villarreal Rodríguez,

Biologist – cytotechnologist.

CONTACT INFORMATION

Medical Diagnostics of Chiriqui

Pathology Laboratory

Office 102, Hospital Chiriqui, South Tower, Third W Ave & Central St, Doleguita, David, province of Chiriqui

Republic of Panama

September, 2016