The phrase "although there were no apparent differences" is correct and usable in written English.
You can use it to introduce a contrast or exception in a discussion where differences are expected but not observed.
Example: "The two products were tested side by side, and although there were no apparent differences, the consumers had strong preferences for one over the other."
Alternatives: "even though no noticeable differences existed" or "despite the lack of visible differences."
Although there were no apparent differences with respect to height and weight, these factors were also adjusted for, as ordered variables, in the main analyses.
Although there were no apparent differences in the risk of stress exposure between the 3 groups examined in this study at discharge, the DSH-R patients may have had a lower stress tolerance or less efficient coping skills.
Children with persistent diarrhoea and without diarrhoea carried a wide range of enteric pathogens, including viruses, bacteria and parasites, and the rates of each varied considerably between studies, although there were no apparent differences between WHO regions.
Although there are no apparent differences, the lower left panel in Figure 3 indicates that there is a larger number of contacts with longer duration.
Although higher infective doses resulted in an earlier induction, there were no apparent differences in time of induction or in strength of induced response between infection with 10×LD50 and 100×LD50 (Figure 4A, left).
There were no apparent differences among the three experimental groups, although weight tended to increase in all groups and temperature to decrease, whilst remaining in the physiological range.
There were no apparent differences due to treatment with tacrolimus.
There were no apparent differences in either macro- or microcirculatory variables between animals attributable to blast exposure, nor in the lactate profile, although further analysis was confounded by the heterogeneity of fluid treatments applied (Additional file 4).
There were no apparent differences between patients receiving RBCs and those receiving other blood products.
There were no apparent differences in diurnal patterns in gs among the treatments.
There were no apparent differences between freeze tolerant and non-freeze tolerant larvae in tracheal displacement or distension of the body during freezing, although there was markedly more distension in D. melanogaster than in C. amoena regardless of diapause state.
