X-ray luminosity as a function of SFR for the sample of galaxies compiled in this work. Black circles correspond to those galaxies with measured X-ray luminosities, while blue triangles represent the detection limits for single sources. These can be regarded as upper limits for the galaxy luminosity in the case it had only one source. The red dashed line (log L_X = log SFR + 39.4) is the relation found by Mineo et al. (2012). It describes well the data at high SFRs, whereas it fails to do so in the opposite SFR range. For log SFR ≲ −1.1, all the data fall above the fit, which suggests the existence of metallicity effects in the sample.