Table 1.
Characteristics of studies included
| First Author | Year | Country | Biomarker | Agea | Proportion of malesa |
Difference in body mass indexb |
Sample size | Effect size | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
|
|||||||||||||
| Control | Diabetic | Zinc | Copper | Ceruloplasmin | Iron | Ferritin | Manganese | |||||||
| Pidduck | 1970 | England | Plasma | 52.95 | 100 | --c | 40 | 36 | 5.71 | 0.18 | -- | -- | -- | -- |
| Pidduck | 1970 | England | Plasma | 57.43 | 0 | -- | 46 | 42 | -4.07 | 1.26 | -- | -- | -- | -- |
| Mateo | 1978 | Spain | Serum | -- | -- | -- | 10 | 49 | 1.2 | 1.29 | 0.39 | -- | -- | -- |
| Raz | 1989 | Israel | Serum | 50.51 | 49.15 | 1.7 | 21 | 38 | 0.58 | -0.9 | -- | -- | -- | -- |
| Car | 1992 | Yugoslavia | Serum | 45.5 | 46.67 | 4.3 | 15 | 15 | −1.42 | −2.86 | -- | -- | -- | -- |
| Williams | 1995 | UK | Plasma | 51.55 | 46.15 | -- | 26 | 26 | −6.09 | −1.99 | -- | -- | -- | -- |
| Hughes | 1998 | Singapore | Serum | -- | 100 | 1.3 | 248 | 72 | -- | -- | -- | -- | 0.44 | -- |
| Hughes | 1998 | Singapore | Serum | -- | 0 | 1.5 | 282 | 54 | -- | -- | -- | -- | 0.46 | -- |
| Daimon | 1998 | Japan | Serum | 57.05 | -- | -- | 158 | 637 | -- | -- | 2.58 | -- | -- | -- |
| Ekmekcioglu | 2000 | Austria | Plasma | 67.05 | -- | 0 | 50 | 53 | 0.31 | 0.2 | -- | --d | -- | 0.2 |
| Kim | 2000 | Korea | Serum | 57.03 | 46.67 | 2.4 | 25 | 50 | -- | -- | -- | -- | 0.32 | -- |
| Olaniyan | 2001 | Nigeria | Serum | 57.03 | 39.81 | -- | 50 | 53 | −0.99 | 0.74 | -- | -- | -- | -- |
| Ekin | 2003 | Turkey | Serum | 56.98 | 0 | 1.2 | 29 | 108 | −4.27 | --d | -- | 5.86 | -- | --d |
| Ekin | 2003 | Turkey | Serum | 56.28 | 100 | 1.6 | 21 | 92 | −4.64 | --d | -- | 4.83 | -- | --d |
| Memisogullari | 2003 | Turkey | Serum | -- | -- | -- | 18 | 21 | -- | -- | 0.86 | -- | -- | -- |
| Memisogullari | 2004 | Turkey | Serum | 54.49 | -- | -- | 21 | 29 | -- | -- | 1.35 | -- | -- | -- |
| Qin | 2004 | China | Serum | -- | -- | -- | 110 | 104 | -- | -- | 2.33 | -- | -- | -- |
| Elis | 2004 | Israel | Serum | 63 | 40.59 | -- | 40 | 29 | -- | -- | -- | −0.04 | 0.15 | -- |
| Jiang | 2004 | USA | Plasma | 56.45 | 0 | 4.1 | 716 | 698 | -- | -- | -- | -- | 0.42 | -- |
| Elsammak | 2005 | Egypt | Serum | -- | -- | -- | 18 | 22 | -- | -- | -- | -- | −1.19 | -- |
| Kaviarasan | 2005 | India | Plasma | 54.24 | -- | 5.21 | 18 | 20 | -- | -- | 3.76 | -- | -- | -- |
| Virgolici | 2005 | Romania | Plasma | 53.4 | 50 | 11.4 | 20 | 20 | -- | -- | 1.02 | -- | -- | -- |
| Al-Maroof | 2006 | Iraq | Serum | 45.73 | -- | 1.69 | 133 | 101 | −1.18 | -- | -- | -- | -- | -- |
| Abou-Shousha | 2006 | Egypt | Serum | 48.52 | 0 | -- | 10 | 20 | -- | -- | -- | -- | 0.65 | -- |
| Lee | 2006 | Korea | Serum | 58.6 | 67.35 | -- | 47 | 48 | -- | -- | -- | 0.15 | 0.86 | -- |
| Adewumi | 2007 | Nigeria | Serum | 46.67 | 100 | 6.25 | 50 | 28 | -- | --d | -- | -- | -- | −0.89 |
| Adewumi | 2007 | Nigeria | Serum | 44.12 | 0 | 3.43 | 40 | 62 | -- | --d | -- | -- | -- | −1.03 |
| Viktorinova | 2009 | Slovak | Plasma | 42.49 | 47.46 | 0.55 | 34 | 25 | −0.49 | 0.53 | -- | -- | -- | -- |
| Rajpathak | 2009 | USA | Serum | 50.3 | 36.4 | 1.5 | 280 | 280 | -- | -- | -- | -- | 0.11 | -- |
| Flores | 2010 | Mexico | Serum | -- | -- | -- | 12 | 76 | 0.04 | 1.05 | -- | -- | -- | 1.15 |
| Sarkar | 2010 | India | Plasma | 54.39 | 62.19 | -- | 78 | 123 | -- | 2.94 | −1.3 | -- | -- | -- |
| Ashourpour | 2010 | Iran | Serum | 53.29 | -- | 0.29 | 53 | 54 | -- | -- | -- | -- | 3.41 | -- |
| Chacko | 2010 | India | Serum | -- | 52.87 | -- | 47 | 40 | -- | -- | 11.13 | -- | -- | -- |
| Nasli-Esfahani | 2011 | Iran | Serum | 50.6 | 34.96 | -- | 151 | 150 | −1.05 | --d | -- | -- | -- | −0.13 |
| Kim | 2011 | Korea | Serum | 51.27 | 100 | 0.8 | 3384 | 727 | -- | -- | -- | -- | 0.3 | -- |
| Kim | 2011 | Korea | Serum | 50.17 | 0 | 2.2 | 3869 | 327 | -- | -- | -- | -- | 0.54 | -- |
| Ferdousi | 2012 | Bangladesh | Serum | -- | -- | 5.15 | 60 | 60 | −0.38 | 0.46 | -- | -- | -- | -- |
| Savu | 2012 | Romania | Plasma | 40.99 | 41 | -- | 15 | 15 | -- | 1.56 | 1.55 | -- | -- | -- |
| Ganesh | 2012 | India | Serum | 42.7 | 38.35 | −1.86 | 30 | 30 | -- | -- | -- | 0.39 | 0.6 | -- |
| Praveeena | 2013 | India | Serum | -- | -- | -- | 40 | 40 | −3.41 | -- | -- | -- | -- | -- |
| Farid | 2013 | Saudi Arabia | Serum | 59.51 | 100 | -- | 55 | 55 | −1.19 | 0.84 | -- | -- | -- | --d |
| Dosa | 2013 | Romania | Plasma | -- | -- | 3.86 | 17 | 30 | −2.53 | 0.44 | -- | -- | -- | -- |
| Kundu | 2013 | India | Serum | -- | -- | 30 | 30 | -- | -- | -- | 0.33 | 2.1 | -- | |
| Santa | 2014 | India | Serum | -- | -- | 5.42 | 40 | 60 | −4.66 | 5.5 | -- | -- | -- | -- |
| Oyedeji | 2014 | Nigeria | Plasma | -- | 0 | -- | 35 | 50 | −2.03 | --d | -- | 2.66 | -- | -- |
| Kumar | 2014 | India | Serum | 48.5 | 74 | -- | 50 | 50 | −1.86 | 2.07 | -- | -- | -- | -- |
| Alam | 2014 | Pakistan | Serum | 40.4 | -- | -- | 44 | 67 | -- | -- | -- | -- | 2.4 | -- |
| Nagarajrao | 2015 | Saudi Arabia | Serum | 49.43 | 55.24 | 0.04 | 58 | 47 | −2.18 | 4.09 | -- | 3.33 | -- | -- |
| Maheshwari | 2015 | India | Serum | 48.28 | 50 | 50 | -- | 2.58 | ||||||
| Badran | 2016 | Egypt | Serum | 52.88 | 57.89 | 0.96 | 36 | 40 | −4.51 | --d | -- | --d | -- | --d |
| Atari-Hajipirlo | 2016 | Iran | Serum | 52.46 | 53.12 | -- | 50 | 46 | −1.25 | 1.21 | -- | 1.35 | -- | -- |
| Wang | 2016 | China | Serum | 67.58 | 100 | 0.87 | 529 | 289 | -- | -- | -- | -- | -- | 0.15 |
| Wang | 2016 | China | Serum | 67.63 | 0 | −2 | 751 | 494 | -- | -- | -- | -- | -- | −0.29 |
| Devi | 2016 | India | Serum | -- | 47.5 | -- | 40 | 40 | −0.67 | 4.06 | -- | -- | -- | -- |
| Goud | 2016 | India | Serum | -- | -- | -- | 20 | 20 | -- | -- | 0.97 | −0.51 | 2.17 | -- |
| Jeppu | 2016 | Malaysia | Serum | -- | -- | -- | 50 | 50 | -- | -- | −2.21 | -- | -- | -- |
| Borah | 2016 | India | Serum | 53.93 | 56.5 | 2.17 | 92 | 92 | -- | -- | -- | -- | 1.87 | -- |
| Eva | 2016 | Banglade | Serum | 47.79 | 54 | 0.36 | 50 | 50 | −0.96 | -- | -- | -- | -- | −0.9 |
| Zhang | 2017 | China | Serum | 55.91 | 34.68 | 1.2 | 1327 | 510 | 0.16 | 0.15 | -- | -- | -- | 0.02 |
a
Represents the weighted average where the weights are the number of individuals in control and diabetic groups
b
Represents the difference in the body mass index between diabetic and control groups
c
Not reported in the primary study
d
Data did not meet the inclusion criteria