Table 4– Summary of studies excluded from meta-analysis

Reason for exclusion	Study design
	Retrospective	Prospective	RCT	DBPCT
No asthma subgroup	Ehrenthal [25], Fell [26], Sheiner [27], Acs [28], Beckmann [29], Littner [30], Liu [31], Demissie [32, 33], Lehrer [34], Getahun [35, 36], Mabie [37], Syed [38], Karimi [39], Carroll [40], Snyder [41], Breton [42, 43], Aly [44] , Almeid [45], Macmullen [46], Blais [47], Clifton [48]	Mihrshahi [49],Greenberger [50],Hendler [51], Savilahti [52]	Wendel [53]
Not subgroup of interest	Alexander [11], Blais [24, 54], Kallen [55], Macmullen [56], Norjavaara [57], Wen [58], Reece [59], Dombrowski [60], Clark [61], Lao [62], Eltonsy [63], Breton [64], Martel [65]	Schatz [15, 66–68], Stenius-Aarniala [69, 70], Minerbi-Codish [71],Moldenhauer [72], Sarkar [73]	Silverman [74]
Inadequately defined subgroup	Kallen [75]	Bracken [9], Triche [76], Doucette 77, Schatz [78], Bakhireva [79]
No comparison group	Olesen [10], Twaites [80]	Bakhireva [81], Dombrowski [82], Bakhireva [83], Schatz [84], Murphy [85], Namazy [86], Clifton [87], Dombrowski [88]		Dombrowski [88]