Abstract
Background:
Liquid-based cytology (LBC) can improve adequacy, monolayer quality with a clean background compared to conventional smears (CS).
Aims and Objectives:
The objective was to compare the quality and diagnostic yield of CS and LBC in routine cytological investigations.
Materials and Methods:
This retrospective study consisted of 306 samples (255 gynecological, 39 nongynecological, and 12 fine needle aspiration cytology [FNAC]) during a 2-year period (2019–2020). From each patient, two samples were collected in the same manner in the same sitting and processed by CS and LBC (ThinPrep® 2000, Hologic Inc.). Both CS and LBC were compared for adequacy, quality, representativeness, inflammation, hemorrhage, necrosis, preservation, reactive changes, organisms, atypia/dysplasia/malignancy, and preparation/screening time. Statistical analysis was performed.
Results:
No statistically significant difference was noted for adequacy, representativeness, reactive changes, preservation, and atypia/dysplasia/malignancy. CS was better in cellularity and diagnosis of inflammation and organisms, whereas LBC had a clean background and the difference was statistically significant (P = 0.0005).
Conclusions:
CS was equivalent to LBC in adequacy, representativeness, reactive changes, and atypia/dysplasia/malignancy. Adequacy comparable to LBC can be achieved in CS by careful sample collection, processing, and screening by trained cytotechnologists. CS was better in detecting organisms and inflammation than LBC. The advantages of LBC were monolayer smear, clean background, and lesser screening time, but the demerit was higher cost and longer processing time. Therefore, LBC is best suited to those laboratories having high sample inadequacy rates, lack of competent cytotechnologists, and no financial constraints. Either man or machine, appropriate and adequate sample collection by trained personnel forms the cornerstone for ensuring adequacy in both CS and LBC.
Keywords: Conventional, cost, cytology, diagnostic yield, LBC, merit, quality
INTRODUCTION
Cytological examinations have been proved useful for the screening, diagnosis, and follow-up of various cancers.[1-4] Conventional smears (CS) pose the limitation of inadequate cellularity, obscuring hemorrhage, inflammation, mucus, and cellular overlapping, resulting in high false-negative rate ranging from 14% to 33%.[3-5]
Liquid-based cytology (LBC) can improve the cellular and diagnostic yield and has completely replaced CS in the western world.[2,3] In LBC, the entire sample (aspirate or cell sediment) is transferred into the preservative vial, whereas in CS, only part of the sample is used while a large portion is discarded. In LBC, a monolayer smear in a limited area is prepared by the machine with a clean background devoid of artifacts, which is lacking in CS. Thus, LBC facilitates better screening and identification of abnormal cells within minimal time and provides sample for ancillary tests such as human papillomavirus (HPV)-DNA and immunostaining.[2-5] The US Food and Drug Administration (US FDA) approved LBC technologies including ThinPrep® and SurePath™. The widespread practice of LBC in low- and middle-income countries (LMIC) is restricted due to the cost factor. Although few low-cost LBC technologies are available, the reduction in cost is marginal.[6,7]
Sample collection by trained personnel forms the cornerstone for ensuring adequacy in both CS and LBC. If cytotechnologists are trained for collection, manual preparation, screening, and interpretation, outcomes similar to LBC can be achieved in CS.
AIMS AND OBJECTIVES
This study was conducted to compare the quality and diagnostic yield of CS and the corresponding LBC at a tertiary oncology institute.
MATERIALS AND METHODS
This retrospective study consisted of 306 samples (255 gynecological and 51 nongynecological samples including 12 fine needle aspiration cytology [FNAC], 17 serous fluids, and 22 bronchial lavage) collected over a period of 2 years (2019–2020). From each patient, two identical samples were collected and processed by CS and LBC. The LBC samples were processed in ThinPrep® 2000 (Trivitron, Hologic Inc.).
CS: Cervicovaginal smears were collected using sterile cotton-tipped applicator sticks by trained cytotechnologists.[8] The FNAC, bronchial lavage, and fluid samples were collected by clinician, pathologist, or radiologist. All CS were prepared by trained cytotechnologists. For FNAC, rapid on-site sample evaluation (ROSE) was done from the first pass. Nongynecological samples (serous fluids and bronchial lavage) were centrifuged at 2000 rpm for 10 min. After decanting the supernatant, the sediment was picked up using a cotton-tipped applicator stick and rolled on the slide to achieve a thin-layer smear.[9] In hemorrhagic samples, one extra smear was subjected to saline rehydration for lysing red blood cells (RBCs).[10]
LBC smear: Cervicovaginal smears were collected by cytotechnologists using the brush provided by the manufacturer. The brush was rinsed quickly into the PreservCyt® vial and swirled vigorously to release the material before discarding the device. All LBC samples were processed by trained cytotechnologists. For FNAC, the material from the second pass was collected in 15 ml of normal saline. FNAC and nongynecological samples (serous fluids and bronchial lavage) were centrifuged at 2000 rpm for 10 min. After decanting the supernatant, 15 ml of Cytolyt™ solution was added to the sediment, mixed, and centrifuged. After decanting the supernatant, the sediment was transferred into the PreservCyt™ vial, kept for 15 min, processed in ThinPrep® 2000, and smears were prepared.
Both CS and LBC smears from each sample were immediately fixed in 100% methanol and subjected to Papanicolaou staining in an auto-stainer. Subsequently, screening and interpretation was done by cytotechnologists followed by pathologists. Original cytodiagnosis was based on the best suitable findings from both CS and LBC.
For the study purpose, trained cytotechnologists and cytopathologists were blinded to both CS and LBC smears, who reviewed and interpreted them as per the standard terminologies. The difference in opinion, if any, was discussed on a multi-head microscope before finalizing the report. Parameters such as adequacy/cellularity, smear quality, representativeness, inflammation, hemorrhage, necrosis, preservation, reactive changes, organisms, atypia/malignancy, and processing/screening time were studied and compared between CS and LBC.
Gynecological smears were considered satisfactory for evaluation when well-preserved/stained squamous epithelial cells (8000–12,000 for CS and >5000 for LBC) were present. Smears were considered unsatisfactory if the requisite number of cells was not present or cellular overlapping, obscuring hemorrhage/inflammation, or air-drying artifacts were present in >80% of the smear.
Nongynecological smears including FNAC were evaluated for adequacy/cellularity and categorized as good (>5000 cells), moderate (approximately 2500 cells), or scant (approximately 500 cells). The presence of even single atypical/dysplastic/malignant cell made the smear adequate.
The monolayer quality and cellular overlapping of CS and LBC were compared by subjective assessment and graded as CS same as LBC (CS = LBC), CS superior to LBC (CS > LBC), or CS inferior to LBC (CS < LBC).
Gynecological smears were evaluated for the presence of transformation zone (TZ) components and nongynecological samples for representativeness of the specific anatomic site.
Presence or absence of inflammation, RBCs, and necrosis was noted. Preservation of morphology, organisms, reactive cellular changes, atypical, dysplastic, or malignant cells, and screening/processing time were documented.
The data was compiled in Statistical Package for the Social Sciences (SPSS) version 25, and statistical analysis was carried out using frequency (%), descriptive statistics, Chi-square test, Fisher’s exact test, and t-test. P value of <0.05 was considered statistically significant.
RESULTS
The study consisted of 306 samples including 255 (83.3%) gynecological, 12 (3.9%) FNAC, and 39 (12.7%) nongynecological samples. Three hundred and five (99.7%) samples were satisfactory for evaluation, whereas one (0.3%) gynecological sample was unsatisfactory due to insufficient squamous epithelial cellularity by both techniques (P = 1.000).
In CS, cellularity was moderate in 305 (99.7%) samples and scant in one (0.3%) sample. In LBC, cellularity was moderate in 268 (87.6%) samples and scant in 38 samples (12.4%) (P = 0.0005). With regard to thin-layer quality, CS = LBC in 59 samples (19.3%), CS > LBC in 49 samples (16%), and LBC > CS in 198 samples (64.7%) (P = 0.0005).
The representative cells were noted in 296 (96.7%) samples by both CS and LBC (P = 1.000). In gynecological samples, TZ components were seen in 217 (85.1%) samples and not seen in 10 samples (3.9%) by both CS and LBC. The remaining 28 (11%) samples were satisfactory for evaluation, but the TZ component was absent as the samples were collected from the vaginal vault (post-hysterectomy). All nongynecological smears were satisfactory for evaluation and showed representative cells from the specific site in both the techniques (P = 1.000).
Inflammation was detected in 281 (91.9%) CS samples compared to 205 (67%) LBC samples [Figure 1 a and b] and the difference was statistically significant (P = 0.0005). RBCs were absent in 229 (74.8%) CS samples, compared to 273 (89.2%) LBC samples (P = 0.0005).
Figure 1.
Cervicovaginal CS shows inflammation (a), whereas corresponding LBC (b) shows clean background with reduced number of WBCs. Cervicovaginal CS showing inflammation and Trichomonas (c), whereas corresponding LBC (d) shows Trichomonas in a clean background (Pap, ×400). CS = conventional smears, LBC = liquid-based cytology
The cell morphology was well preserved in all samples, and none of the samples showed necrosis, air-drying, or degenerative changes by either CS or LBC. The statistical analysis was not possible due to identical results in both.
Reactive changes were detected in 220 (71.9%) CS samples and 218 (71.2%) LBC samples (P = 0.929). In gynecological samples, reactive changes were seen in 193 (75.7%) CS samples compared to 191 (74.9%) LBC samples (P = 0.918). In nongynecological samples reactive changes were present in 27 samples (52.9%) and absent in 24 samples by both CS and LBC (47.1%) (P = 1.000).
Organisms were identified in 243 (79.4%) CS samples compared to 186 (60.8%) LBC samples (P = 0.0005). In gynecological samples, Doderlein bacilli, coccobacilli, Candida, or Trichomonas were detected in 243 (95.3%) CS samples compared to 186 (72.9%) LBC samples. Doderlein bacilli were noted in 95 CS samples and corresponding 92 samples of LBC preparation; in three LBC samples, it was absent. Bacterial vaginosis was noted in 141 CS and 87 LBC samples and was absent in the remaining 54 LBC samples. Candida was noted in four cases each of CS and LBC. Both bacterial vaginosis and Candida were noted in one case each of CS and LBC. Bacterial vaginosis and Trichomonas were noted in two cases each of CS and LBC [Figure 1c and d]. No organism was identified in 12 cases by both methods.
Atypical/malignant cells were detected in 45 (14.7%) CS samples compared to 43 (14.1%) LBC samples (P = 0.908).
In gynecological samples, epithelial cell abnormality (ECA) was detected in 23 (9%) CS samples compared to 21 (8.2%) LBC samples [Table 1]. Atypical squamous cells of undetermined significance (ASC-US) was detected in nine CS samples, where the corresponding LBC showed ASC-US in seven samples and low-grade squamous intraepithelial lesion (LSIL) and negative for ECA in one each. LSIL was detected in 11 CS samples, where the corresponding LBC showed LSIL in 10 samples [Figures 2a–d and 3a, b] and negative for ECA in one sample [Table 1]. One case each of ASC-H, high-grade squamous intraepithelial lesion (HSIL), and adenocarcinoma was detected in both CS and LBC [Figure 3c and d]. ECA was absent in 232 (90.98%) CS samples compared to 234 (91.76%) LBC samples (P = 0.875).
Table 1.
ECA in gynecological samples – CS versus LBC
| Conventional n=255 | LBC | ||||||
|---|---|---|---|---|---|---|---|
|
| |||||||
| NILM | ASC-US | LSIL | ASC-H | HSIL | Ad Ca | ||
| NILM | 232 | 232 | - | - | - | - | - |
| ASC-US | 7+1a+1b | 1a | 7 | 1b | - | - | - |
| LSIL | 10+1c | 1c | - | 9 | - | - | - |
| ASC-H | 1 | - | - | - | 1 | - | - |
| HSIL | 1 | - | - | - | - | 1 | - |
| Ad Ca | 1 | - | - | - | - | - | 1 |
Ad Ca=adenocarcinoma, ASC-H=atypical squamous cell – cannot exclude high-grade squamous intraepithelial lesion, ASC-US=atypical squamous cells of undetermined significance, CS=conventional smears, ECA=epithelial cell abnormality, HSIL=high-grade squamous intraepithelial lesion, LBC=liquid-based cytology, LSIL=low-grade squamous intraepithelial lesion, NILM=negative for intraepithelial lesion or malignancy. aSamples which were ASC-US on CS and NILM on LBC. bSamples which were ASC-US on CS and LSIL on LBC. cSamples which were LSIL on CS and NILM on LBC
Figure 2.
Cervicovaginal CS shows ASC-US (a), whereas the corresponding LBC (b) shows LSIL. Both CS (c) and the corresponding LBC (d) from cervicovaginal sample show ASC-US (Pap, ×400). ASC-US = atypical squamous cells of undetermined significance, CS = conventional smears, LBC = liquid-based cytology, LSIL = low-grade squamous intraepithelial lesion
Figure 3.
Both CS (a) and the corresponding LBC (b) from cervicovaginal sample show LSIL with koilocytes. Both CS (c) and the corresponding LBC (d) from cervicovaginal sample show HSIL (Pap, ×400). CS = conventional smears, HSIL = high-grade squamous intraepithelial lesion, LBC = liquid-based cytology, LSIL = low-grade squamous intraepithelial lesion
The correlation between cytology and histology findings for both gynecological and nongynecological samples has been presented in detail in Tables 2 and 3.
Table 2.
Cytology–histology correlation of gynecological samples (n=255)
| Conventional | LBC | Histology | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
|
||||||||||||||
| NILM | ASC-US | LSIL | ASC-H | HSIL | Ad Ca | Inad | Neg | CIN I | CIN II | CIN III | Sq Ca | Ad Ca | Not done | ||
| NILM | 232 | 231 | - | 1 | - | - | - | 1 | 21 | 6 | - | - | - | - | 204 |
| ASC-US | 9 | 1 | 7 | 1 | - | - | - | - | 2 | 1 | 1 | - | - | - | 5 |
| LSIL | 11 | 1 | - | 10 | - | - | - | - | 5 | 1 | 1 | - | - | - | 4 |
| ASC-H | 1 | - | - | - | 1 | - | - | - | - | - | 1 | - | - | - | - |
| HSIL | 1 | - | - | - | - | 1 | - | - | - | - | - | - | 1 | - | - |
| Ad Ca | 1 | - | - | - | - | - | 1 | - | - | - | - | - | - | 1 | - |
Ad Ca=adenocarcinoma, ASC-H=atypical squamous cell – cannot exclude high-grade squamous intraepithelial lesion, ASC-US=atypical squamous cells of undetermined significance, CS=conventional smears, HSIL=high-grade squamous intraepithelial lesion, LBC=liquid-based cytology, LSIL=low-grade squamous intraepithelial lesion, NILM=negative for intraepithelial lesion or malignancy, Sq Ca=squamous carcinoma, CIN=Cervical intra-epithelial neoplasia
Table 3.
Cytology–histology correlation of nongynecological samples (n=51)
| Sample | CS | LBC | Histology | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
|
|
|||||||||
| Neg | Atyp | Pos | Neg | Atyp | Pos | Inad | Neg | Atyp | Pos | Not done | |
| Bronchial lavage (22) | 24 | 1 | 7 | 14 | 1 | 7 | 1 | 2 | - | 11 | 8 |
| Serous fluids (17) | 6 | 2 | 9 | 6 | 2 | 9 | 3 | 5 | 1 | 8 | - |
| FNAC (12) | 6 | - | 6 | 9 | - | 3 | - | - | 3 | 4 | 5 |
Atyp=atypia, CS=conventional smears, FNAC=fine needle aspiration cytology, Inad=inadequate, LBC=liquid-based cytology, Neg=negative for malignancy, Pos=positive for malignancy
In nongynecological samples, atypical/malignant cells were detected in 22 (43.1%) samples by both CS and LBC [Table 4]. Three cases each of atypia-not otherwise specified, squamous carcinoma [Figure 4a and b], and non-small cell carcinoma, one case each of primitive neuroectodermal tumor [Figure 4c and d], atypia-suspect malignancy, and follicular lesion, and eight cases of adenocarcinoma were detected by both CS and LBC. One case each of spindle cell tumor and small cell carcinoma were detected in CS, but not in LBC. In 29 cases, CS was negative for atypia/malignancy, which matched with 28 LBC, whereas one LBC showed adenocarcinoma. In short, CS was superior in two cases, whereas LBC was superior in one case (P = 1.000).
Table 4.
Atypical/malignancy in nongynecological samples – CS versus LBC
| Diagnosis | CS | LBC | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
|
| |||||||||||
| Neg | Atyp NOS | Susp malig | Ad Ca | Sq Ca | NSCLC | SCLC | SCT | PNET | FL | ||
| Neg | 29 | 28 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 |
| Atyp-NOS | 3 | 0 | 3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Susp malig | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Ad Ca | 8 | 0 | 0 | 0 | 8 | 0 | 0 | 0 | 0 | 0 | 0 |
| Sq Ca | 3 | 0 | 0 | 0 | 0 | 3 | 0 | 0 | 0 | 0 | 0 |
| NSCLC | 3 | 0 | 0 | 0 | 0 | 0 | 3 | 0 | 0 | 0 | 0 |
| SCLC | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| SCT | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| PNET | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 |
| FL | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Total | 51 | 28 | 3 | 1 | 1 | 3 | 3 | 0 | 0 | 1 | 1 |
Ad Ca=adenocarcinoma, Atyp-NOS=atypia-not otherwise specified, CS=conventional smears, FL=follicular lesion, LBC=liquid-based cytology, Neg=negative for malignancy, NSCLC=non-small cell lung cancer, PNET=primitive neuroectodermal tumor, SCLC=small cell lung cancer, SCT=spindle cell tumor, Sq Ca=squamous carcinoma, Susp malig=suspicious of malignancy
Figure 4.
Both CS (a) and the corresponding LBC (b) show PNET in a pleural fluid sample. Both CS (c) and the corresponding LBC (d) from bronchial lavage sample show squamous carcinoma (Pap, ×400). CS = conventional smears, LBC = liquid-based cytology, PNET = primitive neuroectodermal tumor
The average screening time/smear for CS was 212.19 (±21.010) s, compared to 53.15 (±5.335) s in LBC (P = 0.0005). In gynecological samples, the average screening time for CS was 209.22 (±18.828) s, compared to 52.43 (±4.837) s in LBC. In nongynecological samples, the average screening time for CS was 227.06 (±24.923) s, compared to 56.76 (±6.231) s in LBC (P = 0.0005).
The average processing time for CS was approximately 15 min per sample. LBC needed 2 min more for the smear preparation of gynecological samples. For nongynecological LBC samples, an additional 10 min for centrifugation and 2 min for smear preparation was needed.
DISCUSSION
The present study that evaluated the difference in diagnostic yield in identical samples processed by CS and LBC based on 12 parameters and six parameters showed statistically significant differences (P = 0.0005). CS was superior in cellularity and detection of inflammation and organisms, whereas LBC was superior in the smear quality, clean background, and screening time. No statistically significant difference was identified in terms of adequacy, presence of TZ/representativeness, reactive changes, and ECA/dysplasia/malignancy. The cells were well preserved, and necrosis was absent in all samples by both the methods [Table 5].
Table 5.
Output and P-value in various parameters between CS and LBC
| Parameter | Output and P (n=306) | ||
|---|---|---|---|
|
| |||
| CS | LBC | P | |
| Sample adequacy | 99.7% | 99.7% | 1.0000 |
| Representativeness | 96.7% | 96.7% | 1.0000 |
| Reactive changes | 71.9% | 71.2 | 0.9290 |
| Atypia/dysplasia/malignancy | 14.7% | 14.1% | 0.9080 |
| Cellularity | 99.7% | 87.6% | 0.0005 |
| Inflammation | 91.9% | 67% | 0.0005 |
| Organisms | 79.4% | 60.8% | 0.0005 |
| Monolayer smear | 16% | 64.7% | 0.0005 |
| Clean background/RBC absent | 74.8% | 89.2% | 0.0005 |
| Average screening time in seconds | 212.19 | 53.15 | 0.0005 |
| Cell preservation | 100% | 100% | Not applicable |
| Necrosis | 0% | 0% | Not applicable |
| Cost/test (Rs.) | Basic cost | Basic cost + Rs. 400/- | Not applicable |
CS=conventional smears, LBC=liquid-based cytology
Many studies have claimed improved adequacy by LBC compared to CS.[4,11-16] A study by Davey et al.[17] showed no significant difference in inadequate smears between CS and LBC. In the present study, 99.7% of samples processed by both the techniques showed adequate cellularity, except a single Pap smear where both CS and LBC were unsatisfactory due to insufficient squamous epithelial cells. This could be attributed to error in collection procedure. The adequacy of CS was achieved by proper sample collection and careful smear preparation by trained cytotechnologists. LBC has the advantage of making adequate smears by mechanically transferring optimum number of cells from the cell suspension on to glass slide. The study results showed that the smear adequacy by manual processing by a trained cytotechnologist matched that of LBC. During sample collection and processing, utmost care had been taken to avoid air-drying and achieve immediate fixation.
The overall cellularity was superior in CS compared to LBC. The gynecological samples did not show any variation in cellularity between CS and LBC [Table 2]. In nongynecological samples, the low cellularity in LBC may be due to dilution of cell content in the collection medium, whereas CS was prepared directly from the concentrated cell sediment. However, none of the cases were nondiagnostic due to low cellularity. Singh et al.[18] have observed reduction of unsatisfactory smears from 4.3% in CS to 1.7% in LBC. The meta-analysis of 25 prospective studies by Bernstein et al.[19] concluded that the ThinPrep® LBC could improve cellular adequacy compared to CS. Hayama et al.[20] demonstrated inadequacy rate of 6.8% in oral CS due to hypocellularity compared to LBC. van Riet et al.[21] showed improved diagnostic accuracy of 16% in LBC compared to CS in Endoscopic Utra-Sound guided-Fine Needle Aspiration Cytology (EUS-FNAC) of pancreatic lesions, especially in the absence of ROSE. In our study, all FNAC samples were collected with ROSE and were comparable in adequacy in both LBC and CS. Bishop, in a study of cellularity of LBC, has stated that false negativity could not be distinguished by cellularity, and that cellularity did not assure adequacy and adequacy should be based on measurement of prevalence of abnormal cells.[22] In the present study, adequacy was evaluated on the basis of representative cells. Cellularity was applied for negative diagnosis, whereas presence of abnormal cells made the smear adequate irrespective of cellularity.
From the present study, it was evident that the difference in cellularity and diagnostic yield between CS and LBC were statistically not significant. This reiterates our view that smear preparation by a trained cytotechnologist can ensure optimal cellularity in CS comparable to LBC. For gynec and FNAC, the first sample collected was for CS followed by the second sample for LBC; whereas fluids and lavages, the sample was divided into two equal portions and processed separately for CS and LBC. There may be a chance of bias as the first sample always yields better cellularity.
The limitation of variation in thickness of CS has totally been eliminated in LBC. The reason for monolayer quality in 64.7% LBC was due to machine processing. The corresponding CS showed thin quality only in 16%. However, CS with almost comparable thin quality as LBC can be achieved by trained cytotechnologists. The preparation of monolayer CS is difficult, but can be achieved to a greater extent by using cotton-tipped applicator stick.[8] Although few overlapping areas were present in CS, the screening and interpretation was not compromised. Hayama et al.,[20] in their study, reported statistically significant overall improvement in smear thickness, distribution of cells, and reduction in cell overlapping in LBC. Thick layer of cells in CS as one of the factors for inadequacy has been documented by Haghighi et al.[23] The present study showed better smear quality in LBC compared to CS.
There was no difference in TZ/representative cells in smears by either method. This was due to proper collection and processing of samples by trained cytotechnologists. Many studies have reported better sampling of TZ components in LBC compared to CS.[4,11-16] TZ components could not be easily identified in CS due to overlapping and thick smears. In LBC, the cleaner background and processing of entire sample enhanced the pick-up and identification of TZ. Bergeron and Fagnani[13] reported presence of endocervical cells in 13% of LBC compared to only 7% in CS. In another study by Strander et al.,[14] the endocervical cells were lacking in LBC compared to CS. In the present study, TZ components were present in 85.1% and absent in 3.9% by both the methods. In 11%, the sample was collected from vaginal vault (post-hysterectomy) and smears represented the site. The manual CS collected with sterilized cotton-tipped applicator sticks was comparable to LBC in terms of TZ, both quantitatively and qualitatively. The nongynecological samples also revealed the presence of representative cells by both the methods.
The presence of inflammation was missed in LBC because of the reduced number of neutrophils. Identification of inflammation in LBC despite reduced number of neutrophils has been reported by some authors, but was not possible in our study.[24]
Compared to CS, complete or almost complete lysis of RBC was noted in LBC smears, resulting in clean background, facilitating faster screening and lesser eye fatigue. In CS of hemorrhagic serous fluids and lavage, one additional smear was processed for lysis of RBC by saline rehydration, which provided an equally clean background for faster screening.[10]
The cell morphology was well preserved in all the samples, and none of the samples showed necrosis, air-drying, or degenerative changes either by CS or LBC. Reactive changes were observed in both CS and LBC, and the difference between the two methods was not statistically significant.
Sherwani et al.[4] reported 8.7% better detection of infectious organisms in LBC compared to 3.1% in CS. The present study showed no significant statistical difference in the detection of organisms by both CS and LBC, except bacterial vaginosis, which was detected more in CS (55%) compared to LBC (34%).
Many studies have documented better detection of ECA/malignancy in LBC compared to CS or good agreement for the detection of ECA between CS and LBC.[21,25-30] In the present study, the difference in the detection rate of ECA/malignancy between the two methodologies was statistically not significant [Tables 2 and 4]. This was probably due to proper collection, preparation, and meticulous screening and careful interpretation by trained cytotechnologists.
The increased processing time for LBC compared to CS has not been reported in literature. Although the processing time of extra 2 min for gynecological and 12 min for nongynecological LBC samples was expendable in small laboratories with minimum workload, it can be an additional burden for large laboratories with a high workload. LBC also required additional training for sample processing and interpretation, besides periodical maintenance and calibration of equipment. Whereas for CS, the sample processing and smear preparation required only a trained cytotechnologist.
Screening time is dependent on the number of diagnostic cells in proportion to normal cells, severity of atypia in diagnostic cells, and distracting background. Higher number of atypical cells takes shorter screening time compared to scant atypical cells, which may take longer especially in a distracting background. The screening time was considerably reduced in LBC obviously because of the small screening area (314 mm2, i.e., 20-mm-diameter area in ThinPrep® LBC compared to 800 mm2, i.e., 40 mm × 20 mm coverslip area in CS), clean background, and uniform monolayer quality of the smear. These findings were in agreement with many other studies.[10,17-19]
CONCLUSIONS
CS was equivalent to LBC in terms of adequacy, representativeness, reactive changes, and atypia/dysplasia/malignancy. Adequacy in CS comparable to LBC can be achieved by careful sample collection, processing, and screening by trained cytotechnologists. The efficacy of CS for detecting organisms and inflammation was better than that of LBC. The advantages of LBC were monolayer smear, clean background, and lesser screening time, but the major demerit was higher cost and longer processing time. Therefore, LBC is best suited to those laboratories having high sample inadequacy rates, lack of competent cytotechnologists, and no financial constraints. Unlike man, machine prepares smears with consistent quality, but adequacy in both CS and LBC depends on appropriate sample collection by trained personnel.
Statement of ethics
This study protocol was reviewed and approved by the Institutional Ethics Committee (approval no.: IRB-3739), Tata Memorial Centre, Mumbai, India.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
Acknowledgements
The authors acknowledge Mr. Amol Bansode, Administrative staff, Department of Cytopathology, Tata Memorial Hospital, Mumbai, for the assistance in statistical analysis of the data.
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