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Lung cancer in elderly patients: the role of induced sputum production to obtain a cytological diagnosis.

Introduction

Sputum cytology is an established technique in the investigation of suspected bronchial carcinoma. The diagnostic sensitivity of this procedure varies, but the more sputum samples that are obtained the better the diagnostic yield. For example one series reported a diagnostic rate for a single adequate sputum sample of 41%, which rose to 85% with four or more daily samples [1]. Multiplication of samples, however, causes a significant strain on the cytology service as an experienced pathologist requires 10-20 minutes to examine each slide [2].

Sputum cytology is now, however, less commonly used, as fibreoptic bronchoscopy has become more widely available and is known to give a high diagnostic yield [3]. However, there remain groups of patients in whom there may be relative contra-indications to bronchoscopy (e.g. older patients, or those with poor respiratory reserve), or where bronchoscopy facilities are not readily available. More recently, the technique of inducing sputum samples by nebulized hypertonic saline has been introduced in the diagnosis of Pneumocystis carinii pneumonia in HIV-positive patients [4]. To determine whether this technique may be useful in diagnosing bronchial carcinoma, we studied 26 elderly patients with suspected lung cancer who all subsequently had a fibreoptic bronchoscopy (FOB).

Patients and Methods

Twenty-six patients were enlisted for this study (20 men, 6 women; mean age 70, range 61-89 years). All were suspected of having bronchial carcinoma and all had abnormal chest radiographs. Twenty-four patients were or had been cigarette smokers. Patients were admitted for fibreoptic bronchoscopy and prior to bronchoscopy an induced sputum sample was obtained, using hypertonic saline (3%) and an ordinary ward nebulizer. This required 20-30 minutes and the help of a chest physiotherapist to ensure an adequate sputum sample. Fibreoptic bronchoscopy was performed using an Olympus FB3 fibrescope and any endobronchial lesion visible was biopsied. If no lesion was identified bronchial washings were taken from the area under suspicion.

All induced sputum samples and bronchoscopic specimens were analysed in the pathology department in the usual way.

Results

Of the 26 patients studied, adequate induced sputum samples were obtained from 24 (92%). Only 1 2 were able to expectorate spontaneously. The technique for inducing samples was well tolerated. At subsequent bronchoscopy a diagnosis of lung cancer was made in 16 of these 24 cases. Of these 16 patients, 11 had a positive diagnosis made on the induced sputum samples obtained prior to bronchoscopy (Table I). Of the three patients who had a mass visible on their chest radiograph and negative fibreoptic bronchoscopy and induced sputum specimens, two had peripheral shadows which were later diagnosed by needle biopsy (1 adenocarcinoma and 1 small cell carcinoma), and on subsequent computerized tomography in the third there was no evidence of a tumour. In the 15 tumours situated centrally (as judged at bronchoscopy), the induced sputum was positive in 8/15(53%). In contrast, in only 1/4 of the peripherally based lesions (25%) was the induced sputum positive.
Table 1. Chest radiograph appearances and results of fibreoptic
bronchoscopy (FOB) and induced sputum (IS) samples in
the 19 patients later shown to have bronchial carcinoma
                                     Diagnosis of bronchial
                                        carcinoma by:
Chest radiograph
appearance         No.               FOB              IS
Mass               15               13              9
Effusion            3                2              1
Collapse            1                1              1
Total              19               16 (84%)       11 (58%)


Of the two patients who had pleural effusions but negative bronchoscopy, pleural aspiration and biopsy revealed tuberculosis (1 case), and adenocarcinoma (1 case). In the two patients who had collapse but no evidence of tumour, later computerized tomography showed no evidence of a mass lesion. One patient who presented with clinical and radiological signs of consolidation was found to have an unresolved pneumonia, which cleared with appropriate antibiotic treatment.

Overall, therefore, a diagnosis of bronchial carcinoma was made in 19/24 patients (79%) in whom a satisfactory induced sputum sample was obtained. Of these 19, a positive diagnosis was made at FOB in 16 (84%) and on the single induced sputum sample in 11 (58%). There were no false positives in the induced sputum samples (100% specificity). The frequency of the different histological types and the diagnostic yield of induced sputum is shown in Table II.
Table II. Sensitivity of induced sputum in different
types of bronchial carcinoma
                                      Positive cytology in
                     Total          induced sputum sample
Squamous cell Ca      13                    8 (62%)
Adenocarcinoma         4                    2 (50%)
Small cell Ca          2                    1 (50%)
Total                 19                    11(58%)


Discussion

The pick-up rate of 58% in this study for a single induced sputum sample is higher than the reported figure of 41 % for single ordinary sputum samples (in patients later proven at thoracotomy or necropsy to have bronchial carcinoma). With four daily induced sputum samples collected over 4 days using an ultrasonic nebulizer, a sensitivity of 84% for bronchial carcinoma has recently been reported [5]. This latter study did not, however, report the sensitivity of a single induced sputum sample. Furthermore, the methods used for obtaining an induced sputum sample were more complicated, requiring an ultrasonic nebulizer, and the patient to be fasted for 12 hours. In the study reported here the patients were not fasted prior to the induced sputum specimen collection and a single sample was obtained using an ordinary ward nebulizer. Using this technique a sensitivity of 58% was obtained in the 24/26 patients who managed to produce a sample

These results suggest that a single induced sputum sample may have a higher diagnostic yield in the diagnosis of bronchial carcinoma than an ordinary sputum sample. This technique may, therefore, be of value in those elderly patients in whom bronchoscopy is relatively contra-indicated and in whom previous ordinary sputum cytology was either negative or no sputum was obtainable. Furthermore, the technique may be more cost-effective than the conventional approach of obtaining multiple ordinary sputum samples for cytological analysis, and may be performed as an outpatient procedure.

Reference

[1.] Oswald NC, Hinson KFW, Canti G, Miller AB. The diagnosis of primary lung cancer with special reference to sputum cytology. Thorax 1971;26:623-31. [2.] Benbassat J, Regev A, Slater PE. Predictive value of sputum cytology. Thorax 1987;42:165 72. [3.] O'Hickey S, Hilton AM. Fibreoptic bronchoscopy in the elderly. Age Ageing 1987;16:229 33. [4.] O'Brien RF, Quinn JL, Miyahara BT, Lepott RB, Conn DL. Diagnosis of Pneumocystis carinii pneumonia by induced sputum in a city with moderate incidence of AIDS. Chest 1989;95:136-8 [5.] Khajotia RR, Mohn A, Pokieser L, Schalleshak J, Vetter N. Induced sputum and cytological diagnosis of lung cancer. Lancet 1991;338:976-7.

Authors' address The Cardiothoracic Centre, Thomas Drive, Liverpool L14 3PE Address correspondence to: Dr C. R. K. Hind
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Author:Jack, C.I.A.; Sheard, J.D.H.; Lippitt, B.; Fromholtz, A.; Evans, C.C.; Hind, C.R.K.
Publication:Age and Ageing
Date:May 1, 1993
Words:1099
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