complex (MAC) is commonly isolated from water, house dust and soil.1
Data on the treatment of pulmonary MAC in HIV-seronegative patients is limited by the paucity of randomised controlled trials (RCTs). Older, non-comparative studies in which patients were treated with combinations of conventional anti-tuberculous agents reported highly variable outcomes. Patients in these studies did not necessarily have uniform definitions of disease, radiographic response or cure. In most cases, conversion of sputum cultures to negative was the primary outcome.1
Sputum conversion rates using standard antituberculous agents, primarily in populations with classic MAC pulmonary disease, ranged from 38–91% across studies published between 1967 and 1988.2–4
A more recent RCT compared 2 years of INH, RFP and EB to 2 years of RFP plus EB in 75 patients from the UK and Scandinavia.5 6
David Griffith and colleagues studied both CAM-based and AZM-based intermittent regimens for treatment of pulmonary MAC disease. Fifty-nine per cent of patients who took daily AZM-based treatment attained treatment success—defined as 12 consecutive months of negative sputum cultures while the patient was on treatment. Fifty-five per cent of patients who took AZM three times weekly along with daily companion drugs and 65% of patients who took all drugs three times weekly met criteria for treatment success. There were no significant differences in the rates of treatment success among these three groups. Furthermore, drug toxicity was significantly less with intermittent administration of AZM.7
Although this patient had been treated with CAM, SM, RFP and EB for 15 years, her disease condition did not improve. AZM three times weekly slightly improved the control of M avium infection. However, she continued to show bloody sputum and high-grade fever and was admitted to our hospital three to five times a year. Furthermore, P aeruginosa was sometimes detected in the sputum. When the left lung bulla wall became thicker, we suspected that the lesion resulted from fungal infection, especially aspergillus. Although aspergillus antigen was negative throughout the clinical course, the value of β-D-glucan slightly increased in inverse proportion to the inflammatory findings of white blood cell count or CRP. With these findings, her complaints of persistent fever and chest pain improved and she has not required hospital admission since then.
β-D-Glucan is a polyglucose compound consisting of a chain of glucopyranosyl rings, united primarily by β-1,3-polyglucoside linkages, and is known as one of the major and common constituents of fungal cell walls of fungi in general.8–10
The assay of β-D-glucan is a promising means for diagnosing fungal diseases.11
False-positive β-D-glucan reactions are known to occur in patients with renal failure who are undergoing haemodialysis with cellulose membranes, patients treated with intravenous immunoglobulins, and specimens or patients exposed to gauze or other materials that contain glucans. Albumin, coagulation factors and plasma protein fraction manufactured by certain vendors for intravenous injection also have been shown to contain high levels of β-D-glucan. High concentrations of bilirubin and triglyceride have been reported to be inhibitory and would cause false-negative results, while haemolysis would also cause false-negative results.12
Our patient had not had recent surgery and had not been exposed to any gauze or other materials that contain glucans, and bilirubin, triglyceride and haemoglobin showed fairly stable normal values after 2007. A study based on autopsy cases reported the positive predictive value of the β-D-glucan test when used in a population where prevalence of fungal infection was 11.8%, and was only 47% even if a cut-off of 30 pg/ml was used.13
As β-D-glucan testing in the study was performed within 2 weeks before death, the disease condition was more severe than in our case. Although the increase of β-D-glucan was only 10–20 pg/ml in this case, the values gradually increased accompanied with left lung mass. Despite no detection of fungus, we suspected fungal infection, which was not demonstrated by aspergillus antigen or antibody but by β-D-glucan, may have suppressed the MAC activity, which is microbial substitution. We did not identify the insidious fungal infection, which was detected only by the increase in β-D-glucan, but it may suppress M avium
or P aeruginosa
We should further investigate the progression of fungal infection or regression of M avium infection.
- Fungal infection may have suppressed the MAC activity.
- In this case we should consider fungal infection with MAC or microbial substitution of fungal infection.
- The insidious fungal infection was detected by the increase in ß-D glucan.