Pneumocystis carinii Pneumonia in Critically Ill Patients with Malignancy: A Descriptive Study

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1 MAJOR ARTICLE Pneumocystis carinii Pneumonia in Critically Ill Patients with Malignancy: A Descriptive Study J. R. Zahar, 1,a M. Robin, 1 E. Azoulay, 2 F. Fieux, 2 G. Nitenberg, 1 and B. Schlemmer 2 1 Intensive Care Department, Institut Gustave-Roussy, and 2 Intensive Care Department, Saint-Louis Teaching Hospitals and University Paris 7, Paris, France There are few data on Pneumocystis carinii pneumonia (PCP) in critically ill human immunodeficiency virus (HIV) negative patients. Improved knowledge of the presenting symptoms of and prognostic factors for PCP may help to reduce the high mortality rate associated with PCP in such patients. We retrospectively studied 39 consecutive patients with acute PCP-related respiratory failure and malignancy who were treated at 2 intensive care units (ICUs) during a 10-year period. Univariate logistic regression identified the following 8 predictors of mortality at 30 days after patient admission to the ICU (30-day mortality rate, 33%): complete remission of the malignancy (odds ratio [OR], 0.18), receipt of 11 course of antimalignancy chemotherapy (OR, 17.2), involvement of 4 lobes noted on a chest radiograph (OR, 5), 115% neutrophils in bronchoalveolar lavage [BAL] fluid specimens (OR, 6), Organ System Failure score (OR, 7.33), Simplified Acute Physiology Score II (OR, 1.12), and the need for either mechanical ventilation (OR, 63) or vasopressors (OR, 25.9). Studies are needed to determine whether aggressive monitoring and treatment of patients with 115% neutrophils in BAL fluid specimens can improve the outcome of critically ill patients with malignancy and PCP. Before the era of AIDS, Pneumocystis carinii pneumonia (PCP) occurred mainly among patients with leukemia, malnutrition, lymphoma, T cell deficiency, or end-stage disease, or among those who had received steroid therapy [1]. Now, given the high mortality rates among HIV-infected patients with PCP who require mechanical ventilation (MV) [2], physicians maintain a high index of suspicion for PCP in patients with respiratory symptoms. However, they tend to rely on diagnostic and prognostic criteria derived from studies of PCP in HIV-positive patients [3]. This can lead physicians to Received 25 January 2002; revised 6 May 2002; electronically published 23 September a Present affiliation: Service de Médecine Interne et Maladies Infectieuses, Centre Hospitalier Quesnay, Mantes, France. Reprints or correspondence: Dr. Jean-Ralph Zahar, Service de Médecine Interne et Maladies Infectieuses, Centre Hospitalier François Quesnay, 2 Blvd. de Sully, Mantes, France (jrzahar@hotmail.com). Clinical Infectious Diseases 2002; 35: by the Infectious Diseases Society of America. All rights reserved /2002/ $15.00 miss PCP in patients with malignancy, for whom the presenting symptoms of PCP can differ markedly from those seen among HIV-positive patients [4 6]. Moreover, recent advances in the treatment of malignancy, including the use of more-intensive chemotherapy, allow patients with malignancy to live longer; however, at the same time, such treatment advances increase patient exposure to disease- and treatment-related lifethreatening complications, including PCP [7, 8]. Acute respiratory failure is a complication of PCP in 5% 30% of cases and is associated with a high risk of in-hospital death [9, 10]. However, few studies have described PCP patterns in critically ill patients with malignancy [11, 12]. Moreover, these studies have included not only patients with malignancy but, also, patients with other causes of immunodeficiency [13]. We retrospectively studied patients with malignancy who were admitted to 2 French intensive care units (ICUs) that followed the same standardized protocol for the management of patients with PCP. We pursued the dual objective of (1) describing patterns of PCP in PCP in Critically Ill Patients with Malignancy CID 2002:35 (15 October) 929

2 patients with malignancy to help physicians make an earlier diagnosis, and (2) identifying predictors of mortality at 30 days after patient admission to the ICU (hereafter known as 30- day mortality ) to assist physicians in selecting the best treatment strategy. PATIENTS AND METHODS We retrospectively reviewed the charts of patients with PCPrelated acute respiratory failure who were admitted to the ICUs of 2 university hospitals between 1 January 1989 and 1 May All patients who had clinical and/or radiological signs of pneumonia and who had positive results of either cytological tests or direct fluorescent antibody staining for P. carinii in samples of induced sputum or bronchoalveolar lavage (BAL) fluid were eligible for inclusion in the study. Data collection. Data on age, sex, and comorbidities were abstracted from each medical record. Also recorded were the antimalignancy treatments that were used in particular, cyclophosphamide, methotrexate, aracytine, fludarabine, highdose steroid therapy (prednisone equivalent, 11 mg/kg/day for 1 month), radiation therapy, and bone marrow transplantation. Adequate PCP prophylaxis was defined as administration of trimethoprim (20 mg/kg/day) plus sulfamethoxazole (100 mg/kg/day) for 3 days a week. The following data also were recorded: time from the onset of symptoms to initiation of specific treatment; patterns noted on chest radiographs; reasons for ICU admission; Simplified Acute Physiology Score II (SAPS II) [14], Organ System Failure (OSF), and Organ Dysfunction and Infection (ODIN) scores at the time of admission to the ICU [15, 16]; the results of routine laboratory tests to determine the lymphocyte count, the lactate dehydrogenase (LDH) level, and the arterial blood gas level while patients were breathing room air at admission; and whether MV was required at admission or within the first 48 h after admission. Recent neutropenia was defined by a neutrophil count of!50 neutrophils/mm 3 within the 10 days before admission. Radiographic patterns were classified as alveolar, alveolar-interstitial, or diffuse interstitial; the presence of pleural effusion and the number of lobes with radiographic involvement were recorded. Shock was defined by the presence of any of the following criteria: a sustained (11-h) decrease of 40 mm Hg in systolic blood pressure (SBP; with the decrease in SBP measured from the SBP noted at baseline), an SBP of!90 mm Hg after adequate fluid replacement, or the need for vasopressors. PCP diagnosis and BAL evaluation. Bronchoscopy with BAL was performed by wedging the bronchoscope into a distal airway of the relevant bronchus (the middle lobe or lingula in patients with diffuse radiographic changes). The BAL fluid was immediately divided into aliquots for examination and culture and was dispatched to a cytology laboratory and a microbiology laboratory. Routine evaluation for P. carinii involved the use of 2 stains (toluidine blue O and May-Grünwald-Giemsa) and a specific immunofluorescence test. A positive result obtained by either method was considered to be evidence of PCP; none of the patients with negative stain results had a positive immunofluorescence test result. BAL fluid was also evaluated for the presence of opportunistic bacteria, viruses, fungi, other protozoa, and acid-fast bacteria. In the cytology laboratory, BAL fluid was cytocentrifuged ( 10 3 cells per slide) and stained with May-Grünwald-Giemsa stain for cell count determination and for cell typing as well as for identification and quantification of P. carinii. Treatment of PCP involved the use of trimethoprim (20 mg/ kg/day) and sulfamethoxazole (100 mg/kg/day). Steroid therapy was added if deemed appropriate by the physician. Statistical analysis. Results are reported either as medians and 25th and 75th percentiles or as proportions. Categorical variables were compared using the x 2 test, and continuous variables were compared using Wilcoxon s rank sum test for unpaired data. Univariate analysis was performed using logistic regression with the 30-day mortality rate as the outcome variable of interest. ORs and their 95% CIs were calculated. Statistical tests were performed using SPSS software, version 8.1 (SPSS). P!.05 was considered statistically significant. RESULTS Characteristics of the patients at admission. During the 16- month study period, 39 patients (20 men and 19 women) were admitted to the participating ICUs for PCP-related acute respiratory failure. For 10 patients, diagnosis was confirmed before admission to the ICU. The median patient age was 52 years (range, years). Twenty-eight patients (72%) had hematological malignancies, 7 (18%) had solid tumors, and 4 (10%) had nonmalignant hematological diseases (table 1). Seven patients (18%) had a history of chronic respiratory failure, and 2 of these 7 patients had chronic renal failure. As shown in table 2, a total of 28 patients (72%) were receiving steroid therapy during hospitalization, and 32 (82%) had received antimalignancy chemotherapy within the past 6 months, with cyclophosphamide as the most commonly used agent (20 [51%] of patients), followed by methotrexate (8 [21%] of patients) and then by aracytine (4 [10%] of patients) and fludarabine (2 [5%] of patients). Five patients (13%) had received radiation therapy directed to the mediastinum. Of the 39 patients evaluated, 4 (10%) had no history of immunosuppressive treatment. Nineteen patients experienced complete remission, and 6 had received a bone marrow transplant. Despite the presence of risk factors for PCP, only 5 patients were receiving adequate prophylaxis. 930 CID 2002:35 (15 October) Zahar et al.

3 Table 1. Underlying malignancies in 39 patients with acute respiratory failure associated with Pneumocystis carinii pneumonia. Hematological malignancy No. of patients Leukemia or lymphoma Non-Hodgkin lymphoma 14 Chronic lymphoid leukemia 5 Hodgkin lymphoma 3 Acute myeloid leukemia 3 Chronic myeloid leukemia 1 Acute plasmocytic leukemia 1 Acute lymphoid leukemia 1 Total 28 Solid tumor Undifferentiated carcinoma 2 Astrocytoma 1 Breast cancer 1 Hydatiform mole 1 Urinary bladder cancer 1 Lung cancer 1 Total 7 Miscellaneous Autoimmune hemolytic anemia 2 Aplastic anemia 1 CD4 lymphopenia 1 Total 4 Characteristics of the acute disease at admission. The median time between diagnosis of the underlying disease and development of PCP (defined as respiratory symptom onset ) was 600 days (range, days). For 3 patients, PCP occurred before they received treatment for malignancy. The median time from respiratory symptom onset to diagnosis of PCP was 7 days (range, 1 64 days). Fever and acute tachypnea were the 2 most common clinical signs at admission (table 3), and only one-third of patients presented with the classic triad of dry cough, dyspnea, and fever. The median lymphocyte count was 800 lymphocytes/mm 3 (range, lymphocytes/ mm 3 ). The median arterial partial pressure of oxygen while patients were breathing room air was 47 mm Hg (range, mm Hg). The median LDH level was 1965 IU/L (range, IU/L). Cytological and microbiological findings. Diagnosis of PCP was made by examination of BAL fluid specimens obtained from 36 patients and induced sputum samples obtained from 3 patients. A high cell count was found in the BAL fluid specimens of 32% of the patients; the median cell count was 180,000 cells/ml (range, 120, ,000 cells/ml). In BAL fluid specimens obtained from 20 patients, 115% of cells were found to be neutrophils. For 11 patients, the number of P. carinii organisms recovered from BAL fluid was very small; for 16, it was small; and for only 9, it was large. Other pathogens were identified in 11 (28%) of the 39 patients (9 patients had pathogenic bacteria and 2 had cytomegalovirus [1 had viremia]). Radiographic findings. Chest radiographs obtained at admission revealed consistently abnormal findings, showing unilateral involvement in 4 patients and bilateral involvement in 35. Radiographic patterns were alveolar-interstitial for 28 patients (72%), interstitial only for 9 patients (23%), and alveolar for 2 patients (5%). Five patients (13%) had pleural effusion. The median number of involved lobes was 2 (range, 1 3). Findings and clinical events. The median SAPS II score at admission was 42 (range, 25 50). All patients had acute respiratory failure at the time of admission to the ICU, and 2 had shock. The median time from respiratory symptom onset to ICU admission was 6 days (range, 0 64 days). Seventeen patients (44%) needed MV, including 13 who needed MV within the first 24 h after admission. Of the 9 patients who received noninvasive MV, 4 subsequently required endotracheal MV. During the ICU stay, shock developed in 11 patients (28%); 8 of these 11 patients had documented bacteremia, whereas 3 had no evidence of infection other than PCP. Three patients (8%) experienced pneumothorax and required chest tube drainage. The median length of stay in the ICU was 7 days (range, 1 56 days). Treatments. All 39 patients received intravenously administered high-dose trimethoprim (20 mg/kg/day) and sulfamethoxazole (100 mg/kg/day) as first-line therapy. Thirty-three patients (85%) received steroid therapy (240 mg/day for 3 days, with the dosage then tapered during the next 10 days, until no therapy was given). For 9 patients, continuous positive airway pressure was delivered within the first 48 h after admission to the ICU; all 9 patients survived, although 4 subsequently required endotracheal MV. Four patients who required MV survived, including 2 patients who needed 17 days of MV. Outcome and prognostic factors. For survivors, the median length of stay in the ICU was 7 days (range, 1 56 days). The crude 30-day mortality rate was 33% (13 deaths). Univariate analysis identified 8 parameters associated with 30-day mortality (table 2). Variables not associated with 30-day mortality included duration of respiratory symptoms, respiratory rate and hypoxemia at admission, receipt of steroids, and occurrence of pneumothorax. DISCUSSION Chagas and Carinii first identified P. carinii in the lungs of rats 180 years ago; 60 years ago, the organism was shown to be the cause of epidemic plasma cell pneumonitis in malnourished or premature infants [1] (from a search of the MEDLINE literature from 1966 through 2001). PCP is an opportunistic infection PCP in Critically Ill Patients with Malignancy CID 2002:35 (15 October) 931

4 Table 2. Predictors of death among 39 critically ill intensive care unit patients who had Pneumocystis carinii pneumonia related acute respiratory failure and malignancy, according to univariate logistic regression. Predictor Patients who survived (n p 26) Patients who died (n p 13) OR (95% CI) P Age, median years (range) 52 (40 60) 48 (40 59) 1.01 ( ).43 Receipt of steroids during hospitalization 16 (62) 12 (92) 7.5 ( ).07 Complete remission 15 (58) 4 (31) 0.18 ( ).02 Receipt of 11 course of chemotherapy 3 (12) 9 (69) 17.2 (3.2 93).0009 Bone marrow transplantation 3 (12) 3 (23) 2.3 ( ).35 Duration of symptoms 11 week 14 (54) 7 (54) 1.48 ( ).56 Respiratory rate 135 breaths/min 7 (27) 2 (15) 0.51 ( ).45 Pao 2 while breathing room air at admission, median mm Hg (range) 65 (52 81) 60 (45 70) 0.99 ( ) Pao 2!50 mm Hg 3 (12) 3 (23) 2.2 ( ).38 Lactate dehydrogenase level 12n a 9 (35) 7 (54) 2.53 ( ).22 Large number of P. carinii bodies detected 5 (19) 6 (46) 5.2 ( ).06 Involvement of 4 lobes on chest radiography 13 (50) 11 (85) 5 ( ) % Neutrophils detected in BAL fluid specimens 10 (38) 10 (77) 6 ( ).04 Prognostic score at admission, median (range) Organ System Failure 0 (0 1) 1 (0.75 2) 7.33 ( ).002 Simplified Acute Physiology Score, version II 30 (21 43) 50 (42 50) 1.12 ( ).01 Organ Dysfunction and Infection 1 (1 1) 3 (1 6) 1.26 ( ).06 Receipt of steroids in the intensive care unit 21 (81) 10 (77) 0.11 ( ).59 Need for mechanical ventilation 4 (15) 12 (92) 63 ( ).0006 Need for vasopressor therapy 2 (8) 9 (69) 25.9 (4 166).0006 Time to administration of TMP-SMX,.62 median no. of days (range) 2 (1 4) 2 (1 5) 1.04 ( ) Pneumothorax 2 (8) 1 (8) 1 (0.8 12).99 Nosocomial infection 6 (24) 7 (54) 3.9 ( ).06 NOTE. Data are the median no. (%) of patients, unless otherwise indicated. BAL, bronchoalveolar lavage; Pao 2, arterial partial pressure of oxygen; TMP-SMX, trimethoprim-sulfamethoxazole. a Greater than twice the range considered normal. that is associated with substantial morbidity and mortality even when it is properly treated [5, 7, 8]. Because PCP is both severe and difficult to diagnose, we undertook this study to delineate the spectrum of features that require a high index of suspicion for this infection. Most of our patients had hematological diseases that were treated with antimalignancy chemotherapy. Only 1 patient had acute lymphoblastic leukemia, the hematological malignancy reported to be associated with the highest PCP attack rates [8]. A possible explanation for this small number of patients with acute lymphoblastic leukemia and PCP is that it is standard practice to routinely administer PCP prophylaxis to patients with acute lymphoblastic leukemia. Conversely, 3 patients had conditions previously found to be associated with a low risk of PCP (2 had chronic hemolytic anemia and 1 had CD4 lymphopenia), an observation possibly related to the increasing use of immunosuppressive agents for patients with these conditions. Hughes et al. [17] reported that the intensity of chemotherapy was directly proportional to the incidence of PCP. Moreover, it has been reported that, in patients with vasculitis and connective tissue diseases, diagnostic suspicion was an important factor in the correct identification of patients with pneumocystosis [13]. Strikingly, in our study focused on patients with malignancy, all patients had a history of receiving high-dose steroid therapy and/or antimalignancy chemotherapy. A worrisome finding is that, despite the presence of multiple major risk factors, only 5 patients (13%), all of whom were bone marrow transplant recipients, were receiving adequate PCP prophylaxis. Clinical presentation of PCP varied widely. The median duration of PCP-related symptoms at the time of diagnosis of PCP was 7 days. Only one-third of the patients evaluated had the triad of fever, dyspnea, and dry cough classically described in HIV-positive patients. Of importance, all patients had abnormal findings noted on chest radiographs. The clinical manifestations of PCP tend to be less acute and CID 2002:35 (15 October) Zahar et al.

5 Table 3. Characteristics of critically ill patients at the time of diagnosis of Pneumocystis carinii pneumonia (PCP). Characteristic Median (range) No. (%) of patients Time from diagnosis of malignancy to development of PCP, no. of days 680 (1 3400) Duration of respiratory symptoms, no. of days 7 (0 64) Clinical feature Cough 22 (56) Fever 30 (70) Dyspnea 30 (77) All 3 13 (34) Biological finding Respiratory rate, breaths/min 30 (20 40) Pao 2, mm Hg 47 (30 110) WBC count, cells/mm ( ) Neutrophil count, neutrophils/mm ( ) Lymphocyte count, lymphocytes/mm ( ) LDH level, IU/L 1 (1 6) Fibrinogen level, g/l 5.3 ( ) BAL fluid specimen finding Cytological analysis Neutrophils, % 20 (0 90) Lymphocytes, % 15 (1 90) Siderophages, % 0.3 (0 90) Microbiological studies Cytomegalovirus 11 (28) Bacteria 5 (13) Fungi 3 (8) Chest radiography finding Interstitial infiltrate 9 (23) Alveolar-interstitial infiltrate 28 (72) Bilateral infiltrate 35 (90) Pleural effusion 5 (13) NOTE. BAL, bronchoalveolar lavage; LDH, lactate dehydrogenase; Pao 2, arterial partial pressure of oxygen. less severe among patients with AIDS, compared with patients with other causes of immunodeficiency [4]. Of interest, 84% of the patients in our study received adjunctive steroid therapy. Whereas this approach has been proven in patients with AIDS who have PCP, it has not been validated in patients with PCP related to other risk factors [11]. In their recent retrospective study of 30 HIV-negative adults with severe PCP, Pareja et al. [12] suggested that high-dose adjunctive steroid therapy possibly accelerated recovery but failed to improve the rates of endotracheal MV and in-hospital mortality. Similarly, we found no difference in the 30-day mortality rate for patients who did or did not receive steroid therapy. However, the data on steroid treatment and severity can be confounded. Few data are available regarding HIV-negative patients admitted to ICUs for PCP. Moreover, factors associated with the prognosis of PCP in ICU patients have been studied only in HIV-positive patients. The present retrospective study sought to identify predictors of 30-day mortality in 39 ICU patients with acute respiratory failure related to PCP. The 30-day mortality rate of 33% in our study is low compared with that of previous studies of PCP in HIV-negative ICU patients. One possible explanation for this low rate is that previous studies included only patients who were receiving MV [12]. Another possible explanation is the high rate of use of noninvasive MV as an alternative to endotracheal MV in our ICU. PCP in Critically Ill Patients with Malignancy CID 2002:35 (15 October) 933

6 The value of a high neutrophil count in BAL fluid specimens for the prediction of 30-day mortality is a striking finding of our study. In theory, recruitment of neutrophils to the air spaces could result either from a concomitant bacterial infection or from early-stage acute respiratory distress syndrome. Only 11 of our 39 patients had BAL fluid tests that were positive for bacteria, and only 3 of these 11 patients had a differential neutrophil count of 115% noted in a BAL fluid specimen. This finding is consistent with previous data for HIV-positive patients and for patients with acute respiratory distress syndrome associated with other causes [18, 19]. In conclusion, PCP remains potentially fatal for patients with malignancy or hematological disease. Our findings highlight the clinical characteristics that may help physicians make an earlier diagnosis of PCP for HIV-negative immunocompromised patients with acute respiratory failure. References 1. Walzer PD, Perl DP, Krogstad DJ, Rawson PG, Schultz MG. Pneumocystis carinii pneumonia in the United States: epidemiologic, diagnostic, and clinical features. Ann Intern Med 1974; 80: Bedos JP, Dumoulin JL, Gachot B, et al. Pneumocystis carinii pneumonia requiring intensive care management: survival and prognostic study in 110 patients with human immunodeficiency virus. Crit Care Med 1999; 27: Forrest DM, Zala C, Djurdjev O, et al. Determinants of short- and long-term outcome in patients with respiratory failure caused by AIDSrelated Pneumocystis carinii pneumonia. Arch Intern Med 1999; 159: Nuesch R, Bellini C, Zimmerli W. Pneumocystis carinii pneumonia in human immunodeficiency virus (HIV) positive and HIV-negative immunocompromised patients. Clin Infect Dis 1999; 29: Yale SH, Limper AH. Pneumocystis carinii pneumonia in patients without acquired immunodeficiency syndrome: associated illness and prior corticosteroid therapy. Mayo Clin Proc 1996; 71: Kovacs JA, Hiemenz JW, Macher AM, et al. Pneumocystis carinii pneumonia: a comparison between patients with the acquired immunodeficiency syndrome and patients with other immunodeficiencies. Ann Intern Med 1984; 100: Sepkowitz KA, Brown AE, Telzak EE, Gottlieb S, Armstrong D. Pneumocystis carinii pneumonia among patients without AIDS at a cancer hospital. JAMA 1992; 267: Sepkowitz KA. Pneumocystis carinii pneumonia in patients without AIDS. Clin Infect Dis 1993; 17(Suppl 2):S Curtis JR, Greenberg DL, Hudson LD, Fisher LD, Krone MR, Collier AC. Changing use of intensive care for HIV-infected patients with Pneumocystis carinii pneumonia. Am J Respir Crit Care Med 1994; 150: Arend SM, Kroon FP, van t Wout JW. Pneumocystis carinii pneumonia in patients without AIDS, 1980 through 1993: an analysis of 78 cases. Arch Intern Med 1995; 155: Delclaux C, Zahar JR, Amraoui G, et al. Corticosteroids as adjunctive therapy for severe Pneumocystis carinii pneumonia in non human immunodeficiency virus infected patients: retrospective study of 31 patients. Clin Infect Dis 1999; 29: Pareja JG, Garland R, Koziel H. Use of adjunctive corticosteroids in severe adult non-hiv Pneumocystis carinii pneumonia. Chest 1998; 113: Ward MM, Donald F. Pneumocystis carinii pneumonia in patients with connective tissue diseases: the role of hospital experience in diagnosis and mortality. Arthritis Rheum 1999; 42: Le Gall JR, Lemeshow S, Saulnier F. A new Simplified Acute Physiology Score (SAPS II) based on a European/North American multicenter study. JAMA 1993; 270: Fery-Lemonnier E, Landais P, Loirat P, Kleinknecht D, Brivet F. Evaluation of severity scoring systems in ICUs translation, conversion and definition ambiguities as a source of inter-observer variability in APACHE II, SAPS and OSF. Intensive Care Med 1995; 21: Fagon JY, Chastre J, Novara A, Medioni P, Gibert C. Characterization of intensive care unit patients using a model based on the presence or absence of organ dysfunctions and/or infection: the ODIN model. Intensive Care Med 1993; 19: Hughes WT, Feldman S, Aur RJ, Verzosa SM, Hustu HO, Simone JV. Intensity of immunosuppressive therapy and the incidence of Pneumocystis carinii pneumonitis. Cancer 1975; 36: Azoulay E, Parrot A, Flahault A, et al. AIDS-related Pneumocystis carinii pneumonia in the era of adjunctive steroids: implication of BAL neutrophilia. Am J Respir Crit Care Med 1999; 160: Matute-Bello G, Liles WC, Radella F II, et al. Neutrophil apoptosis in the acute respiratory distress syndrome. Am J Respir Crit Care Med 1997; 156: CID 2002:35 (15 October) Zahar et al.