Examining clinical similarities between myalgic encephalomyelitis/chronic fatigue syndrome and d -lactic acidosis: a systematic review

Table 3 Frequency of episodes that reported matching and/or ambiguous/other d-lactic acidosis (d-la) symptoms as a function of age and sex

ME/CFS ICC	d-La symptom overlap with ME/CFS	Episode frequencies
		Paediatric (≤17 years)							Adult (≥18 years)						Total
		Male (15 episodes)		Female (6 episodes)		NI (1 episode)	Total (22 episodes)		Male (20 episodes)		Female (17 episodes)		Total (37 episodes)		(59 episodes)
		n	%	n	%	n	n	%	n	%	n	%	n	%	n	%
A. Postexertional neuroimmune exhaustion	Matching	8	53.3	1	16.7	–	9	40.9	2	20.0	4	23.5	6	16.2	15	25.4
A. Postexertional neuroimmune exhaustion	Ambiguous/other	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
B. Neurological impairments	Matching	12	80.0	6	100	1	19	86.4	18	90.0	15	88.3	33	89.2	52	88.1
	Ambiguous/other	11	73.3	2	33.3	1	14	63.6	17	85.0	14	82.4	31	83.8	45	76.3
	Ambiguous/other B1–B4	3	20.0	1	16.7	1	5	22.7	11	55.0	6	35.3	17	45.9	22	37.3
	Speech/language	7	46.7	2	33.3	1	10	45.5	11	55.0	9	52.9	20	54.1	30	50.8
	Consciousness	5	33.3	–	–	–	5	22.7	5	25.0	3	17.6	8	21.6	13	22.0
C. Immune, gastrointestinal, genitourinary impairments	Matching	3	20.0	–	–	–	3	13.6	6	30.0	4	23.5	9	24.3	12	20.3
C. Immune, gastrointestinal, genitourinary impairments	Ambiguous/other	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
D. Energy production/transportation impairments	Matching	8	53.3	3	50.0	–	11	50.0	7	35.0	2	11.8	9	24.3	20	33.9
D. Energy production/transportation impairments	Ambiguous/other	–	–	–	–	–	–	–	2	10.0	–	–	2	5.4	2	3.4
Mood/behavior	Matching	2	13.3	1	16.7	–	3	13.6	2	10.0	3	17.6	5	13.5	8	13.6
Mood/behavior	Ambiguous/other	6	40.0	–	–	–	6	27.3	4	20.0	3	17.6	7	18.9	13	22.0
Uncategorized d-la symptoms
	Metabolic acidosis	15	100	6	100	1	22	100	20	100	16	94.1	36	97.3	58	98.3
	Other abnormalities	4	26.7	–	–	–	4	18.2	6	30.0	2	11.8	7	18.9	11	18.6

Percentages were calculated from fractions of the number of episodes that reported relevant symptoms (n) against the number of possible episodes (noted in column subheadings) within each sex and age category. ME/CFS broad category B Neurological impairments are highlighted as the primary focus of this review. The ambiguous/other symptoms are further delineated into three subcategories (ICC criteria B1–B4, speech/language symptoms, and level of consciousness; see Table 2 for explanations). In each subcategory the same episode code number can be shown several times to represent multiple symptoms during each d-la episode. See Additional file 2: Table S2 for an expansion of these results showing episode code numbers that were included for each symptom category
Ambiguous/other symptoms that were not clearly identified as consistent with ME/CFS presentation (see Table 2 for detailed symptom delineation), B1–B4 neurocognitive impairments, pain, sleep disturbances, neurosensory and perceptual, motor disturbances, d-la d-lactic acidosis, ICC International Consensus Criteria, Matching mapped overlap between ME/CFS and d-la symptoms, ME/CFS myalgic encephalomyelitis/chronic fatigue syndrome, NI sex not identified