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Communications to the Editor |

Sialyl Lewis X-i Antigen in Pleural Effusion Sialyl Lewis X-i Antigen in Pleural Effusion FREE TO VIEW

Hiroaki Satoh, MD; Hiroichi Ishikawa, MD; Yuko T. Yamashita, MD
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Affiliations: University of Tsukuba, Tsukuba-City, Japan ,  Veterans General Hospital-Taipei, Taipei, Taiwan

Correspondence to: Hiroaki Satoh, MD, Division of Respiratory Medicine, Institute of Clinical Medicine, University of Tsukuba, Tsukuba-City, Ibaraki, 305-8575, Japan; e-mail: hirosato@md.tsukuba.ac.jp



Chest. 1999;116(2):582-583. doi:10.1378/chest.116.2.582-a
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To the Editor:

We read with interest the report by Lee and colleagues (December 1998)1on the usefulness of sialyl stage-specific embryonic antigen-1 (sialyl Lewis X-i antigen). We also have studied and published articles on the clinical utility of the antigen.25 The determination of the cutoff value for their study according to the mean ± SD seems inappropriate because confirmation of the “normal distribution” is not warranted. We believe that receiver operating characteristic (ROC) curve analysis is one of the suitable methods for determination of the cutoff value.

We can share the authors’ observation that “pleural sialyl Lewis X-i antigen levels > 265 U/mL were considered to indicate a diagnosis of adenocarcinoma of the lung.” Our results showed, however, that levels ≥ 214 U/mL were found only in patients with adenocarcinomas that had been proven by cytologic examinations of pleural effusions. This level accounted for 95% specificity. Our study included data from malignant pleural effusions resulting from metastatic adenocarcinomas of organs other than the lung.

Lee, YC, Chen, JH, Lai, SL, et al (1998) Sialyl stage-specific embryonic antigen-1: a useful marker for differentiating the etiology of pleural effusion.Chest114,1542-1545. [CrossRef]
 
Satoh, H, Ishikawa, H, Kamma, H, et al Serum sialyl Lewis X-i antigen levels in non-small cell lung cancer; correlation with distant metastasis and survival.Clin Cancer Res1997;3,495-499
 
Ishikawa, H, Satoh, H, Kamma, H, et al Elevated sialyl Lewis X-i antigen levels in pleural effusions.Intern Med1997;36,685-689. [CrossRef]
 
Satoh, H, Ishikawa, H, Kamma, H, et al Elevated serum sialyl Lewis X-i antigen levels in non-small cell lung cancer with metastasis.Respiration1988;64,295-298
 
Satoh, H, Ishikawa, H, Yamashita, YT, et al Predictive value of preoperative serum sialyl Lewis X-i antigen levels in non-small cell lung cancer.Anticancer Res1998;18,2865-2868
 

Sialyl Lewis X-i Antigen in Pleural Effusion

To the Editor:

We would like to reply to the comments on our article (December 1998)1 by Satoh and colleagues. They suggest that the receiver operating characteristics (ROC) curve analysis appears to be one of the suitable methods to be used for the determination of a cutoff value, unless normal distribution of the data is confirmed.

To the best of our knowledge, there is no standard method for the determination of a cutoff value for a tumor marker. The selection of a cutoff point is dependent mainly on clinical significance. To avoid false-positive results, the highest value obtained from benign cases may be chosen as a cutoff point. In this setting, the specificity appears to be 100%, but at the expense of sensitivity. To increase the sensitivity, a lower value may be used as the cutoff value, but at the expense of specificity.

In our study, the value given by the mean + 2SD of pleural fluid sialyl stage-specific embryonic antigen (SSEA)-1 was selected as a cutoff point because the data were found to be normally distributed in each subgroup (groups 3 to 6) of our benign cases.1 It is plausible that the data are normally distributed when these cases (groups 3 to 6) are pooled as one group. Unfortunately, the data are almost but not quite normally distributed. The ROC curve analysis is used as suggested to determine the cutoff value: 295 U/mL instead of 265 U/mL. When 295 U/mL is used as the cutoff point, the sensitivity and specificity are 64% and 96%, respectively. The sensitivity and specificity are 64% and 95%, respectively, when 265 U/mL is used as the cutoff point. In terms of sensitivity and specificity, the ROC curve analysis adds little value. This supports the notion that the method used in our study for the determination of the cutoff value is adequate.

The clinical significance of the cutoff values selected by either method, mean + 2SD or ROC curve analysis, is comparable in our study. However, we agree that the ROC curve analysis is one of the suitable methods to be used to determine the cutoff point of pleural fluid sialyl SSEA-1.

References
Lee, YC, Chern, JH, Lai, SL, et al Sialyl stage-specific embryonic antigen-1: a useful marker for differentiating the etiology of pleural effusion.Chest1998;114,1542-1545. [CrossRef]
 

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References

Lee, YC, Chen, JH, Lai, SL, et al (1998) Sialyl stage-specific embryonic antigen-1: a useful marker for differentiating the etiology of pleural effusion.Chest114,1542-1545. [CrossRef]
 
Satoh, H, Ishikawa, H, Kamma, H, et al Serum sialyl Lewis X-i antigen levels in non-small cell lung cancer; correlation with distant metastasis and survival.Clin Cancer Res1997;3,495-499
 
Ishikawa, H, Satoh, H, Kamma, H, et al Elevated sialyl Lewis X-i antigen levels in pleural effusions.Intern Med1997;36,685-689. [CrossRef]
 
Satoh, H, Ishikawa, H, Kamma, H, et al Elevated serum sialyl Lewis X-i antigen levels in non-small cell lung cancer with metastasis.Respiration1988;64,295-298
 
Satoh, H, Ishikawa, H, Yamashita, YT, et al Predictive value of preoperative serum sialyl Lewis X-i antigen levels in non-small cell lung cancer.Anticancer Res1998;18,2865-2868
 
Lee, YC, Chern, JH, Lai, SL, et al Sialyl stage-specific embryonic antigen-1: a useful marker for differentiating the etiology of pleural effusion.Chest1998;114,1542-1545. [CrossRef]
 
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