The pooled results indicate relatively

The pooled results indicate relatively low diagnostic sensitivity of 0.70, and specificity of 0.83, suggesting a relatively high rate of missed diagnoses (30%) and misdiagnoses (17%). Likelihood ratios >10 and <0.1 are considered as strong indicators to rule in or rule out a diagnosis, respectively (Deeks and Altman, 2004). In the present meta-analysis, PLR was 4.04 and NLR was 0.36, suggesting relatively low ability to discriminate sarcoidosis from non-sarcoidosis, although the AUC in SROC analysis was relatively high (0.84). While it appears the BALF CD4/CD8 ratio is not robust enough on its own to diagnose sarcoidosis, pooled DOR was moderate (11.17), suggesting that it may be a helpful ancillary tool that, when interpreted together with other diagnostic factors, can improve sarcoidosis diagnosis. QUADAS-2 was used to assess methodological quality of the studies included in our meta-analysis. QUADAS-2 provides more detailed and rigorous assessment than the earlier QUADAS, such as in the explanation of indeterminate results. Although this instrument can be used to assign quality scores (Whiting et al., 2003), it is fundamentally a qualitative tool, which we used to characterize risk of bias along four domains as low, high, or unclear. This analysis suggested quality differences among the included studies, and meta-regression suggested that study quality may have affected the reported diagnostic performance of the BALF CD4/CD8 ratio. In addition, diagnostic performance of the BALF CD4/CD8 ratio was variable even among studies at low risk of bias. These findings highlight the need for better-designed diagnostic studies, particularly prospective studies and studies with low risk of bias. These studies should carefully address the issue of variability of the BALF CD4/CD8 ratio as a diagnostic tool. The studies included in this meta-analysis varied in their cut-off values for the CD4/CD8 ratio, which usually fell between 2 and 4. No international standards exist about what cut-off value to use, and this value is likely to vary with clinical context, depending on country, ethnicity, examination equipment, disease severity, and history of corticosteroid treatment. Our meta-regression of cut-off values suggests that different cut-off values did not substantially affect the diagnostic accuracy of the BALF CD4/CD8 ratio (P=0.57, Table 2). This contrasts with previous studies showing that a CD4/CD8 ratio≥3.5 strongly suggests sarcoidosis, but is not specific enough on its own to diagnose the disease (Marruchella and Tondini, 2002; Costabel et al., 2010). Further work should aim to identify the cut-off value that provides optimal diagnostic accuracy, and researchers should be open to the possibility that different cut-offs are needed for different types of patients or clinical contexts. In addition, all included studies utilized flow cytometry to determine the BALF CD4/CD8 ratio based on a protocol developed for peripheral blood samples. Several studies have reported that flow cytometric typing of order GW5074 from BALF correlates well with results from conventional immunocytochemistry (Brandt et al., 1996; Ma et al., 2001; Smith et al., 2006b; Szpechcinski et al., 2011), though the results may depend on combinations of antibodies and gating strategies. Therefore future studies are needed to optimize these parameters for typing lymphocytes in BALF. There are several factors that should be addressed which may influence the BALF CD4/CD8 ratio. One factor is smoking, which is associated with higher total cell number, higher proportions of CD8+ lymphocytes and CD4+ cells, and lower CD4+/CD8+ ratio in BALF (Hoser et al., 1999). Numbers of CD4+ and CD8+ cells in BALF are also affected in smokers with comorbidities such as chronic obstructive pulmonary disease (Forsslund et al., 2014). Several studies included in this meta-analysis reported smoking history, while its effect on BALF CD4/CD8 ratio remains unclear (Korosec et al., 2010; Fireman et al., 2006). Future studies should examine the potential impact of smoking on BALF cell numbers and proportions, and thereby on the potential diagnostic usefulness of the BALF CD4/CD8 ratio. Another factor was the stage of sarcoidosis. As pulmonary sarcoidosis advances from stage I to stage III, the number of CD8+ cells increases and the number of CD4+ cells decreases, leading to a decrease in the CD4/CD8 ratio (Danila et al., 2008). Indeed, previous work has shown that the diagnostic sensitivity of the BALF CD4/CD8 ratio decreases with increasing stage of sarcoidosis (Danila et al., 2009a); on the other hand, the ratio may be less clinically useful in stage I disease, for which clinical and radiographic features on their own show high diagnostic reliability. A third factor that should be addressed is the recovery rate of BALF, which has been reported to range widely from 23.3% to 91.3% (Fireman et al., 2006; Winterbauer et al., 1993). Most studies included in our meta-analysis did not report the recovery rate, which may bias diagnostic accuracy. A fourth factor was whether or not participants were on corticosteroid treatment, which can modify lymphocyte proportions in BALF and thereby the BALF CD4/CD8 ratio (Danila et al., 2009b). Indeed, some studies suggest that this ratio shows lower diagnostic sensitivity in patients on such treatment (Danila et al., 2009a; He et al., 1994). None of the patients in nine studies (eight publications) received corticosteroids (Suchankova et al., 2013; De Smet et al., 2010; Korosec et al., 2010; Yao et al., 2008; Heron et al., 2008; Fireman et al., 2006; Fireman et al., 1999; Winterbauer et al., 1993), while the other studies did not report corticosteroid status (Lee et al., 2015; von Bartheld et al., 2013; Hyldgaard et al., 2012; Smith et al., 2006a; Greco et al., 2005; Marruchella and Tondini, 2002). Future studies should take into account possible confounding by smoking status, recovery rate, and corticosteroid treatment when assessing the diagnostic performance of BALF CD4/CD8 ratio. Studies should also look systematically at whether the ratio is more clinically useful for advanced stages of the disease, where clinical and radiographic features on their own can be less informative.